diff --git a/resources/celerity/map.php b/resources/celerity/map.php
--- a/resources/celerity/map.php
+++ b/resources/celerity/map.php
@@ -10,7 +10,7 @@
     'conpherence.pkg.css' => '3c8a0668',
     'conpherence.pkg.js' => '020aebcf',
     'core.pkg.css' => 'b797945d',
-    'core.pkg.js' => 'f9c2509b',
+    'core.pkg.js' => 'eaca003c',
     'differential.pkg.css' => '8d8360fb',
     'differential.pkg.js' => '67e02996',
     'diffusion.pkg.css' => '42c75c37',
@@ -178,7 +178,7 @@
     'rsrc/css/phui/workboards/phui-workboard-color.css' => 'e86de308',
     'rsrc/css/phui/workboards/phui-workboard.css' => '74fc9d98',
     'rsrc/css/phui/workboards/phui-workcard.css' => '9e9eb0df',
-    'rsrc/css/phui/workboards/phui-workpanel.css' => 'c5b408ad',
+    'rsrc/css/phui/workboards/phui-workpanel.css' => 'e5461a51',
     'rsrc/css/sprite-login.css' => '18b368a6',
     'rsrc/css/sprite-tokens.css' => 'f1896dc5',
     'rsrc/css/syntax/syntax-default.css' => '055fc231',
@@ -408,15 +408,16 @@
     'rsrc/js/application/phortune/phortune-credit-card-form.js' => 'd12d214f',
     'rsrc/js/application/policy/behavior-policy-control.js' => '0eaa33a9',
     'rsrc/js/application/policy/behavior-policy-rule-editor.js' => '9347f172',
-    'rsrc/js/application/projects/WorkboardBoard.js' => '9d59f098',
+    'rsrc/js/application/projects/WorkboardBoard.js' => 'ba6e36b0',
     'rsrc/js/application/projects/WorkboardCard.js' => '0392a5d8',
     'rsrc/js/application/projects/WorkboardCardTemplate.js' => '2a61f8d4',
-    'rsrc/js/application/projects/WorkboardColumn.js' => 'ec5c5ce0',
+    'rsrc/js/application/projects/WorkboardColumn.js' => 'c344eb3c',
     'rsrc/js/application/projects/WorkboardController.js' => '42c7a5a7',
+    'rsrc/js/application/projects/WorkboardDropEffect.js' => '101121be',
     'rsrc/js/application/projects/WorkboardHeader.js' => '111bfd2d',
-    'rsrc/js/application/projects/WorkboardHeaderTemplate.js' => 'b65351bd',
+    'rsrc/js/application/projects/WorkboardHeaderTemplate.js' => 'ebe83a6b',
     'rsrc/js/application/projects/WorkboardOrderTemplate.js' => '03e8891f',
-    'rsrc/js/application/projects/behavior-project-boards.js' => '412af9d4',
+    'rsrc/js/application/projects/behavior-project-boards.js' => 'cd7c9d4f',
     'rsrc/js/application/projects/behavior-project-create.js' => '34c53422',
     'rsrc/js/application/projects/behavior-reorder-columns.js' => '8ac32fd9',
     'rsrc/js/application/releeph/releeph-preview-branch.js' => '75184d68',
@@ -437,7 +438,7 @@
     'rsrc/js/application/uiexample/notification-example.js' => '29819b75',
     'rsrc/js/core/Busy.js' => '5202e831',
     'rsrc/js/core/DragAndDropFileUpload.js' => '4370900d',
-    'rsrc/js/core/DraggableList.js' => '8bc7d797',
+    'rsrc/js/core/DraggableList.js' => 'c9ad6f70',
     'rsrc/js/core/Favicon.js' => '7930776a',
     'rsrc/js/core/FileUpload.js' => 'ab85e184',
     'rsrc/js/core/Hovercard.js' => '074f0783',
@@ -657,7 +658,7 @@
     'javelin-behavior-phuix-example' => 'c2c500a7',
     'javelin-behavior-policy-control' => '0eaa33a9',
     'javelin-behavior-policy-rule-editor' => '9347f172',
-    'javelin-behavior-project-boards' => '412af9d4',
+    'javelin-behavior-project-boards' => 'cd7c9d4f',
     'javelin-behavior-project-create' => '34c53422',
     'javelin-behavior-quicksand-blacklist' => '5a6f6a06',
     'javelin-behavior-read-only-warning' => 'b9109f8f',
@@ -729,13 +730,14 @@
     'javelin-view-renderer' => '9aae2b66',
     'javelin-view-visitor' => '308f9fe4',
     'javelin-websocket' => 'fdc13e4e',
-    'javelin-workboard-board' => '9d59f098',
+    'javelin-workboard-board' => 'ba6e36b0',
     'javelin-workboard-card' => '0392a5d8',
     'javelin-workboard-card-template' => '2a61f8d4',
-    'javelin-workboard-column' => 'ec5c5ce0',
+    'javelin-workboard-column' => 'c344eb3c',
     'javelin-workboard-controller' => '42c7a5a7',
+    'javelin-workboard-drop-effect' => '101121be',
     'javelin-workboard-header' => '111bfd2d',
-    'javelin-workboard-header-template' => 'b65351bd',
+    'javelin-workboard-header-template' => 'ebe83a6b',
     'javelin-workboard-order-template' => '03e8891f',
     'javelin-workflow' => '958e9045',
     'maniphest-report-css' => '3d53188b',
@@ -761,7 +763,7 @@
     'phabricator-diff-changeset-list' => '04023d82',
     'phabricator-diff-inline' => 'a4a14a94',
     'phabricator-drag-and-drop-file-upload' => '4370900d',
-    'phabricator-draggable-list' => '8bc7d797',
+    'phabricator-draggable-list' => 'c9ad6f70',
     'phabricator-fatal-config-template-css' => '20babf50',
     'phabricator-favicon' => '7930776a',
     'phabricator-feed-css' => 'd8b6e3f8',
@@ -860,7 +862,7 @@
     'phui-workboard-color-css' => 'e86de308',
     'phui-workboard-view-css' => '74fc9d98',
     'phui-workcard-view-css' => '9e9eb0df',
-    'phui-workpanel-view-css' => 'c5b408ad',
+    'phui-workpanel-view-css' => 'e5461a51',
     'phuix-action-list-view' => 'c68f183f',
     'phuix-action-view' => 'aaa08f3b',
     'phuix-autocomplete' => '8f139ef0',
@@ -1001,6 +1003,10 @@
       'javelin-workflow',
       'phuix-icon-view',
     ),
+    '101121be' => array(
+      'javelin-install',
+      'javelin-dom',
+    ),
     '111bfd2d' => array(
       'javelin-install',
     ),
@@ -1227,15 +1233,6 @@
       'javelin-behavior',
       'javelin-uri',
     ),
-    '412af9d4' => array(
-      'javelin-behavior',
-      'javelin-dom',
-      'javelin-util',
-      'javelin-vector',
-      'javelin-stratcom',
-      'javelin-workflow',
-      'javelin-workboard-controller',
-    ),
     '4234f572' => array(
       'syntax-default-css',
     ),
@@ -1593,14 +1590,6 @@
       'javelin-dom',
       'javelin-typeahead-normalizer',
     ),
-    '8bc7d797' => array(
-      'javelin-install',
-      'javelin-dom',
-      'javelin-stratcom',
-      'javelin-util',
-      'javelin-vector',
-      'javelin-magical-init',
-    ),
     '8c2ed2bf' => array(
       'javelin-behavior',
       'javelin-dom',
@@ -1725,18 +1714,6 @@
       'javelin-uri',
       'phabricator-textareautils',
     ),
-    '9d59f098' => array(
-      'javelin-install',
-      'javelin-dom',
-      'javelin-util',
-      'javelin-stratcom',
-      'javelin-workflow',
-      'phabricator-draggable-list',
-      'javelin-workboard-column',
-      'javelin-workboard-header-template',
-      'javelin-workboard-card-template',
-      'javelin-workboard-order-template',
-    ),
     '9f081f05' => array(
       'javelin-behavior',
       'javelin-dom',
@@ -1885,9 +1862,6 @@
       'javelin-stratcom',
       'javelin-dom',
     ),
-    'b65351bd' => array(
-      'javelin-install',
-    ),
     'b7b73831' => array(
       'javelin-behavior',
       'javelin-dom',
@@ -1906,6 +1880,18 @@
       'javelin-uri',
       'phabricator-notification',
     ),
+    'ba6e36b0' => array(
+      'javelin-install',
+      'javelin-dom',
+      'javelin-util',
+      'javelin-stratcom',
+      'javelin-workflow',
+      'phabricator-draggable-list',
+      'javelin-workboard-column',
+      'javelin-workboard-header-template',
+      'javelin-workboard-card-template',
+      'javelin-workboard-order-template',
+    ),
     'bdce4d78' => array(
       'javelin-install',
       'javelin-util',
@@ -1930,15 +1916,17 @@
       'javelin-dom',
       'phuix-button-view',
     ),
+    'c344eb3c' => array(
+      'javelin-install',
+      'javelin-workboard-card',
+      'javelin-workboard-header',
+    ),
     'c3703a16' => array(
       'javelin-behavior',
       'javelin-aphlict',
       'phabricator-phtize',
       'javelin-dom',
     ),
-    'c5b408ad' => array(
-      'phui-workcard-view-css',
-    ),
     'c687e867' => array(
       'javelin-behavior',
       'javelin-dom',
@@ -1978,6 +1966,24 @@
       'javelin-util',
       'phabricator-keyboard-shortcut-manager',
     ),
+    'c9ad6f70' => array(
+      'javelin-install',
+      'javelin-dom',
+      'javelin-stratcom',
+      'javelin-util',
+      'javelin-vector',
+      'javelin-magical-init',
+    ),
+    'cd7c9d4f' => array(
+      'javelin-behavior',
+      'javelin-dom',
+      'javelin-util',
+      'javelin-vector',
+      'javelin-stratcom',
+      'javelin-workflow',
+      'javelin-workboard-controller',
+      'javelin-workboard-drop-effect',
+    ),
     'cf32921f' => array(
       'javelin-behavior',
       'javelin-dom',
@@ -2038,6 +2044,9 @@
       'javelin-dom',
       'javelin-history',
     ),
+    'e5461a51' => array(
+      'phui-workcard-view-css',
+    ),
     'e562708c' => array(
       'javelin-install',
     ),
@@ -2068,14 +2077,12 @@
       'javelin-install',
       'javelin-event',
     ),
+    'ebe83a6b' => array(
+      'javelin-install',
+    ),
     'ec4e31c0' => array(
       'phui-timeline-view-css',
     ),
-    'ec5c5ce0' => array(
-      'javelin-install',
-      'javelin-workboard-card',
-      'javelin-workboard-header',
-    ),
     'ee77366f' => array(
       'aphront-dialog-view-css',
     ),
diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -4094,6 +4094,7 @@
     'PhabricatorProjectDefaultController' => 'applications/project/controller/PhabricatorProjectDefaultController.php',
     'PhabricatorProjectDescriptionField' => 'applications/project/customfield/PhabricatorProjectDescriptionField.php',
     'PhabricatorProjectDetailsProfileMenuItem' => 'applications/project/menuitem/PhabricatorProjectDetailsProfileMenuItem.php',
+    'PhabricatorProjectDropEffect' => 'applications/project/icon/PhabricatorProjectDropEffect.php',
     'PhabricatorProjectEditController' => 'applications/project/controller/PhabricatorProjectEditController.php',
     'PhabricatorProjectEditEngine' => 'applications/project/engine/PhabricatorProjectEditEngine.php',
     'PhabricatorProjectEditPictureController' => 'applications/project/controller/PhabricatorProjectEditPictureController.php',
@@ -10219,6 +10220,7 @@
     'PhabricatorProjectDefaultController' => 'PhabricatorProjectBoardController',
     'PhabricatorProjectDescriptionField' => 'PhabricatorProjectStandardCustomField',
     'PhabricatorProjectDetailsProfileMenuItem' => 'PhabricatorProfileMenuItem',
+    'PhabricatorProjectDropEffect' => 'Phobject',
     'PhabricatorProjectEditController' => 'PhabricatorProjectController',
     'PhabricatorProjectEditEngine' => 'PhabricatorEditEngine',
     'PhabricatorProjectEditPictureController' => 'PhabricatorProjectController',
diff --git a/src/applications/project/controller/PhabricatorProjectBoardViewController.php b/src/applications/project/controller/PhabricatorProjectBoardViewController.php
--- a/src/applications/project/controller/PhabricatorProjectBoardViewController.php
+++ b/src/applications/project/controller/PhabricatorProjectBoardViewController.php
@@ -540,8 +540,8 @@
       ->setExcludedProjectPHIDs($select_phids);
 
     $templates = array();
-    $column_maps = array();
     $all_tasks = array();
+    $column_templates = array();
     foreach ($visible_columns as $column_phid => $column) {
       $column_tasks = $column_phids[$column_phid];
 
@@ -606,18 +606,28 @@
             'pointLimit' => $column->getPointLimit(),
           ));
 
+      $card_phids = array();
       foreach ($column_tasks as $task) {
         $object_phid = $task->getPHID();
 
         $card = $rendering_engine->renderCard($object_phid);
         $templates[$object_phid] = hsprintf('%s', $card->getItem());
-        $column_maps[$column_phid][] = $object_phid;
+        $card_phids[] = $object_phid;
 
         $all_tasks[$object_phid] = $task;
       }
 
       $panel->setCards($cards);
       $board->addPanel($panel);
+
+      $drop_effects = $column->getDropEffects();
+      $drop_effects = mpull($drop_effects, 'toDictionary');
+
+      $column_templates[] = array(
+        'columnPHID' => $column_phid,
+        'effects' => $drop_effects,
+        'cardPHIDs' => $card_phids,
+      );
     }
 
     $order_key = $this->sortKey;
@@ -661,9 +671,9 @@
       'headers' => $headers,
       'headerKeys' => $header_keys,
       'templateMap' => $templates,
-      'columnMaps' => $column_maps,
       'orderMaps' => $vector_map,
       'propertyMaps' => $properties,
+      'columnTemplates' => $column_templates,
 
       'boardID' => $board_id,
       'projectPHID' => $project->getPHID(),
diff --git a/src/applications/project/icon/PhabricatorProjectDropEffect.php b/src/applications/project/icon/PhabricatorProjectDropEffect.php
new file mode 100644
--- /dev/null
+++ b/src/applications/project/icon/PhabricatorProjectDropEffect.php
@@ -0,0 +1,45 @@
+<?php
+
+final class PhabricatorProjectDropEffect
+  extends Phobject {
+
+  private $icon;
+  private $color;
+  private $content;
+
+  public function setIcon($icon) {
+    $this->icon = $icon;
+    return $this;
+  }
+
+  public function getIcon() {
+    return $this->icon;
+  }
+
+  public function setColor($color) {
+    $this->color = $color;
+    return $this;
+  }
+
+  public function getColor() {
+    return $this->color;
+  }
+
+  public function setContent($content) {
+    $this->content = $content;
+    return $this;
+  }
+
+  public function getContent() {
+    return $this->content;
+  }
+
+  public function toDictionary() {
+    return array(
+      'icon' => $this->getIcon(),
+      'color' => $this->getColor(),
+      'content' => hsprintf('%s', $this->getContent()),
+    );
+  }
+
+}
diff --git a/src/applications/project/order/PhabricatorProjectColumnHeader.php b/src/applications/project/order/PhabricatorProjectColumnHeader.php
--- a/src/applications/project/order/PhabricatorProjectColumnHeader.php
+++ b/src/applications/project/order/PhabricatorProjectColumnHeader.php
@@ -9,6 +9,7 @@
   private $name;
   private $icon;
   private $editProperties;
+  private $dropEffects = array();
 
   public function setOrderKey($order_key) {
     $this->orderKey = $order_key;
@@ -64,6 +65,15 @@
     return $this->editProperties;
   }
 
+  public function addDropEffect(PhabricatorProjectDropEffect $effect) {
+    $this->dropEffects[] = $effect;
+    return $this;
+  }
+
+  public function getDropEffects() {
+    return $this->dropEffects;
+  }
+
   public function toDictionary() {
     return array(
       'order' => $this->getOrderKey(),
@@ -71,6 +81,7 @@
       'template' => hsprintf('%s', $this->newView()),
       'vector' => $this->getSortVector(),
       'editProperties' => $this->getEditProperties(),
+      'effects' => mpull($this->getDropEffects(), 'toDictionary'),
     );
   }
 
diff --git a/src/applications/project/order/PhabricatorProjectColumnOrder.php b/src/applications/project/order/PhabricatorProjectColumnOrder.php
--- a/src/applications/project/order/PhabricatorProjectColumnOrder.php
+++ b/src/applications/project/order/PhabricatorProjectColumnOrder.php
@@ -196,6 +196,10 @@
       ->setOrderKey($this->getColumnOrderKey());
   }
 
+  final protected function newEffect() {
+    return new PhabricatorProjectDropEffect();
+  }
+
   final public function toDictionary() {
     return array(
       'orderKey' => $this->getColumnOrderKey(),
diff --git a/src/applications/project/order/PhabricatorProjectColumnOwnerOrder.php b/src/applications/project/order/PhabricatorProjectColumnOwnerOrder.php
--- a/src/applications/project/order/PhabricatorProjectColumnOwnerOrder.php
+++ b/src/applications/project/order/PhabricatorProjectColumnOwnerOrder.php
@@ -122,16 +122,23 @@
       $header_key = $this->newHeaderKeyForOwnerPHID($owner_phid);
 
       $owner_image = null;
+      $effect_content = null;
       if ($owner_phid === null) {
         $owner = null;
         $sort_vector = $this->newSortVectorForUnowned();
         $owner_name = pht('Not Assigned');
+
+        $effect_content = pht('Remove task assignee.');
       } else {
         $owner = idx($owner_users, $owner_phid);
         if ($owner) {
           $sort_vector = $this->newSortVectorForOwner($owner);
           $owner_name = $owner->getUsername();
           $owner_image = $owner->getProfileImageURI();
+
+          $effect_content = pht(
+            'Assign task to %s.',
+            phutil_tag('strong', array(), $owner_name));
         } else {
           $sort_vector = $this->newSortVectorForOwnerPHID($owner_phid);
           $owner_name = pht('Unknown User ("%s")', $owner_phid);
@@ -159,6 +166,14 @@
             'value' => $owner_phid,
           ));
 
+      if ($effect_content !== null) {
+        $header->addDropEffect(
+          $this->newEffect()
+            ->setIcon($owner_icon)
+            ->setColor($owner_color)
+            ->setContent($effect_content));
+      }
+
       $headers[] = $header;
     }
 
diff --git a/src/applications/project/order/PhabricatorProjectColumnPriorityOrder.php b/src/applications/project/order/PhabricatorProjectColumnPriorityOrder.php
--- a/src/applications/project/order/PhabricatorProjectColumnPriorityOrder.php
+++ b/src/applications/project/order/PhabricatorProjectColumnPriorityOrder.php
@@ -65,6 +65,14 @@
       $icon_view = id(new PHUIIconView())
         ->setIcon($priority_icon, $priority_color);
 
+      $drop_effect = $this->newEffect()
+        ->setIcon($priority_icon)
+        ->setColor($priority_color)
+        ->setContent(
+          pht(
+            'Change priority to %s.',
+            phutil_tag('strong', array(), $priority_name)));
+
       $header = $this->newHeader()
         ->setHeaderKey($header_key)
         ->setSortVector($sort_vector)
@@ -73,7 +81,8 @@
         ->setEditProperties(
           array(
             'value' => (int)$priority,
-          ));
+          ))
+        ->addDropEffect($drop_effect);
 
       $headers[] = $header;
     }
diff --git a/src/applications/project/order/PhabricatorProjectColumnStatusOrder.php b/src/applications/project/order/PhabricatorProjectColumnStatusOrder.php
--- a/src/applications/project/order/PhabricatorProjectColumnStatusOrder.php
+++ b/src/applications/project/order/PhabricatorProjectColumnStatusOrder.php
@@ -72,6 +72,14 @@
       $icon_view = id(new PHUIIconView())
         ->setIcon($status_icon, $status_color);
 
+      $drop_effect = $this->newEffect()
+        ->setIcon($status_icon)
+        ->setColor($status_color)
+        ->setContent(
+          pht(
+            'Change status to %s.',
+            phutil_tag('strong', array(), $status_name)));
+
       $header = $this->newHeader()
         ->setHeaderKey($header_key)
         ->setSortVector($sort_vector)
@@ -80,7 +88,8 @@
         ->setEditProperties(
           array(
             'value' => $status_key,
-          ));
+          ))
+        ->addDropEffect($drop_effect);
 
       $headers[] = $header;
     }
diff --git a/src/applications/project/storage/PhabricatorProjectColumn.php b/src/applications/project/storage/PhabricatorProjectColumn.php
--- a/src/applications/project/storage/PhabricatorProjectColumn.php
+++ b/src/applications/project/storage/PhabricatorProjectColumn.php
@@ -218,6 +218,41 @@
       $this->getProject()->getID());
   }
 
+  public function getDropEffects() {
+    $effects = array();
+
+    $proxy = $this->getProxy();
+    if ($proxy && $proxy->isMilestone()) {
+      $effects[] = id(new PhabricatorProjectDropEffect())
+        ->setIcon($proxy->getProxyColumnIcon())
+        ->setColor('violet')
+        ->setContent(
+          pht(
+            'Move to milestone %s.',
+            phutil_tag('strong', array(), $this->getDisplayName())));
+    } else {
+      $effects[] = id(new PhabricatorProjectDropEffect())
+        ->setIcon('fa-columns')
+        ->setColor('blue')
+        ->setContent(
+          pht(
+            'Move to column %s.',
+            phutil_tag('strong', array(), $this->getDisplayName())));
+    }
+
+
+    if ($this->canHaveTrigger()) {
+      $trigger = $this->getTrigger();
+      if ($trigger) {
+        foreach ($trigger->getDropEffects() as $trigger_effect) {
+          $effects[] = $trigger_effect;
+        }
+      }
+    }
+
+    return $effects;
+  }
+
 
 /* -(  PhabricatorConduitResultInterface  )---------------------------------- */
 
diff --git a/src/applications/project/storage/PhabricatorProjectTrigger.php b/src/applications/project/storage/PhabricatorProjectTrigger.php
--- a/src/applications/project/storage/PhabricatorProjectTrigger.php
+++ b/src/applications/project/storage/PhabricatorProjectTrigger.php
@@ -170,6 +170,19 @@
     return $this->triggerRules;
   }
 
+  public function getDropEffects() {
+    $effects = array();
+
+    $rules = $this->getTriggerRules();
+    foreach ($rules as $rule) {
+      foreach ($rule->getDropEffects() as $effect) {
+        $effects[] = $effect;
+      }
+    }
+
+    return $effects;
+  }
+
   public function getRulesDescription() {
     $rules = $this->getTriggerRules();
     if (!$rules) {
diff --git a/src/applications/project/trigger/PhabricatorProjectTriggerInvalidRule.php b/src/applications/project/trigger/PhabricatorProjectTriggerInvalidRule.php
--- a/src/applications/project/trigger/PhabricatorProjectTriggerInvalidRule.php
+++ b/src/applications/project/trigger/PhabricatorProjectTriggerInvalidRule.php
@@ -19,4 +19,8 @@
     return array();
   }
 
+  protected function newDropEffects($value) {
+    return array();
+  }
+
 }
diff --git a/src/applications/project/trigger/PhabricatorProjectTriggerManiphestStatusRule.php b/src/applications/project/trigger/PhabricatorProjectTriggerManiphestStatusRule.php
--- a/src/applications/project/trigger/PhabricatorProjectTriggerManiphestStatusRule.php
+++ b/src/applications/project/trigger/PhabricatorProjectTriggerManiphestStatusRule.php
@@ -38,4 +38,21 @@
     );
   }
 
+  protected function newDropEffects($value) {
+    $status_name = ManiphestTaskStatus::getTaskStatusName($value);
+    $status_icon = ManiphestTaskStatus::getStatusIcon($value);
+    $status_color = ManiphestTaskStatus::getStatusColor($value);
+
+    $content = pht(
+      'Change status to %s.',
+      phutil_tag('strong', array(), $status_name));
+
+    return array(
+      $this->newEffect()
+        ->setIcon($status_icon)
+        ->setColor($status_color)
+        ->setContent($content),
+    );
+  }
+
 }
diff --git a/src/applications/project/trigger/PhabricatorProjectTriggerRule.php b/src/applications/project/trigger/PhabricatorProjectTriggerRule.php
--- a/src/applications/project/trigger/PhabricatorProjectTriggerRule.php
+++ b/src/applications/project/trigger/PhabricatorProjectTriggerRule.php
@@ -40,6 +40,7 @@
   abstract public function getDescription();
   abstract protected function assertValidRuleValue($value);
   abstract protected function newDropTransactions($object, $value);
+  abstract protected function newDropEffects($value);
 
   final public function getDropTransactions($object, $value) {
     return $this->newDropTransactions($object, $value);
@@ -86,4 +87,12 @@
     return $this->getObject()->getApplicationTransactionTemplate();
   }
 
+  final public function getDropEffects() {
+    return $this->newDropEffects($this->getValue());
+  }
+
+  final protected function newEffect() {
+    return new PhabricatorProjectDropEffect();
+  }
+
 }
diff --git a/src/applications/project/trigger/PhabricatorProjectTriggerUnknownRule.php b/src/applications/project/trigger/PhabricatorProjectTriggerUnknownRule.php
--- a/src/applications/project/trigger/PhabricatorProjectTriggerUnknownRule.php
+++ b/src/applications/project/trigger/PhabricatorProjectTriggerUnknownRule.php
@@ -19,4 +19,8 @@
     return array();
   }
 
+  protected function newDropEffects($value) {
+    return array();
+  }
+
 }
diff --git a/webroot/rsrc/css/phui/workboards/phui-workpanel.css b/webroot/rsrc/css/phui/workboards/phui-workpanel.css
--- a/webroot/rsrc/css/phui/workboards/phui-workpanel.css
+++ b/webroot/rsrc/css/phui/workboards/phui-workpanel.css
@@ -178,3 +178,39 @@
   margin-left: 36px;
   overflow: hidden;
 }
+
+.workboard-drop-preview {
+  pointer-events: none;
+  position: absolute;
+  bottom: 12px;
+  right: 12px;
+  width: 300px;
+  border-radius: 3px;
+  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.15);
+  border: 1px solid {$lightblueborder};
+  padding: 4px 0;
+}
+
+.workboard-drop-preview:hover {
+  opacity: 0.25;
+}
+
+.workboard-drop-preview li {
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  margin: 4px 8px;
+  color: {$greytext};
+}
+
+.workboard-drop-preview li .phui-icon-view {
+  position: relative;
+  display: inline-block;
+  text-align: center;
+  width: 24px;
+  height: 18px;
+  padding-top: 6px;
+  border-radius: 3px;
+  background: {$bluebackground};
+  margin-right: 6px;
+}
diff --git a/webroot/rsrc/js/application/projects/WorkboardBoard.js b/webroot/rsrc/js/application/projects/WorkboardBoard.js
--- a/webroot/rsrc/js/application/projects/WorkboardBoard.js
+++ b/webroot/rsrc/js/application/projects/WorkboardBoard.js
@@ -39,6 +39,8 @@
     _columns: null,
     _headers: null,
     _cards: null,
+    _dropPreviewNode: null,
+    _dropPreviewListNode: null,
 
     getRoot: function() {
       return this._root;
@@ -180,6 +182,8 @@
           list.setCompareOnReorder(true);
         }
 
+        list.setTargetChangeHandler(JX.bind(this, this._didChangeDropTarget));
+
         list.listen('didDrop', JX.bind(this, this._onmovecard, list));
 
         lists.push(list);
@@ -190,23 +194,89 @@
       }
     },
 
-    _findCardsInColumn: function(column_node) {
-      return JX.DOM.scry(column_node, 'li', 'project-card');
-    },
+    _didChangeDropTarget: function(src_list, src_node, dst_list, dst_node) {
+      var node = this._getDropPreviewNode();
 
-    _onmovecard: function(list, item, after_node, src_list) {
-      list.lock();
-      JX.DOM.alterClass(item, 'drag-sending', true);
+      if (!dst_list) {
+        // The card is being dragged into a dead area, like the left menu.
+        JX.DOM.remove(node);
+        return;
+      }
+
+      if (dst_node === false) {
+        // The card is being dragged over itself, so dropping it won't
+        // affect anything.
+        JX.DOM.remove(node);
+        return;
+      }
 
       var src_phid = JX.Stratcom.getData(src_list.getRootNode()).columnPHID;
-      var dst_phid = JX.Stratcom.getData(list.getRootNode()).columnPHID;
+      var dst_phid = JX.Stratcom.getData(dst_list.getRootNode()).columnPHID;
 
-      var item_phid = JX.Stratcom.getData(item).objectPHID;
-      var data = {
-        objectPHID: item_phid,
-        columnPHID: dst_phid,
-        order: this.getOrder()
-      };
+      var src_column = this.getColumn(src_phid);
+      var dst_column = this.getColumn(dst_phid);
+
+      var effects = [];
+
+      if (src_column !== dst_column) {
+        effects = effects.concat(dst_column.getDropEffects());
+      }
+
+      var context = this._getDropContext(dst_node);
+      if (context.headerKey) {
+        var header = this.getHeaderTemplate(context.headerKey);
+        effects = effects.concat(header.getDropEffects());
+      }
+
+      if (!effects.length) {
+        JX.DOM.remove(node);
+        return;
+      }
+
+      var items = [];
+      for (var ii = 0; ii < effects.length; ii++) {
+        var effect = effects[ii];
+        items.push(effect.newNode());
+      }
+
+      JX.DOM.setContent(this._getDropPreviewListNode(), items);
+
+      document.body.appendChild(node);
+    },
+
+    _getDropPreviewNode: function() {
+      if (!this._dropPreviewNode) {
+        var attributes = {
+          className: 'workboard-drop-preview'
+        };
+
+        var content = [
+          this._getDropPreviewListNode()
+        ];
+
+        this._dropPreviewNode = JX.$N('div', attributes, content);
+      }
+
+      return this._dropPreviewNode;
+    },
+
+    _getDropPreviewListNode: function() {
+      if (!this._dropPreviewListNode) {
+        var attributes = {};
+        this._dropPreviewListNode = JX.$N('ul', attributes);
+      }
+
+      return this._dropPreviewListNode;
+    },
+
+    _findCardsInColumn: function(column_node) {
+      return JX.DOM.scry(column_node, 'li', 'project-card');
+    },
+
+    _getDropContext: function(after_node, item) {
+      var header_key;
+      var before_phid;
+      var after_phid;
 
       // We're going to send an "afterPHID" and a "beforePHID" if the card
       // was dropped immediately adjacent to another card. If a card was
@@ -231,26 +301,28 @@
 
       if (after_data) {
         if (after_data.objectPHID) {
-          data.afterPHID = after_data.objectPHID;
+          after_phid = after_data.objectPHID;
         }
       }
 
-      var before_data;
-      var before_card = item.nextSibling;
-      while (before_card) {
-        before_data = JX.Stratcom.getData(before_card);
-        if (before_data.objectPHID) {
-          break;
-        }
-        if (before_data.headerKey) {
-          break;
+      if (item) {
+        var before_data;
+        var before_card = item.nextSibling;
+        while (before_card) {
+          before_data = JX.Stratcom.getData(before_card);
+          if (before_data.objectPHID) {
+            break;
+          }
+          if (before_data.headerKey) {
+            break;
+          }
+          before_card = before_card.nextSibling;
         }
-        before_card = before_card.nextSibling;
-      }
 
-      if (before_data) {
-        if (before_data.objectPHID) {
-          data.beforePHID = before_data.objectPHID;
+        if (before_data) {
+          if (before_data.objectPHID) {
+            before_phid = before_data.objectPHID;
+          }
         }
       }
 
@@ -265,12 +337,44 @@
       }
 
       if (header_data) {
-        var header_key = header_data.headerKey;
-        if (header_key) {
-          var properties = this.getHeaderTemplate(header_key)
-            .getEditProperties();
-          data.header = JX.JSON.stringify(properties);
-        }
+        header_key = header_data.headerKey;
+      }
+
+      return {
+        headerKey: header_key,
+        afterPHID: after_phid,
+        beforePHID: before_phid
+      };
+    },
+
+    _onmovecard: function(list, item, after_node, src_list) {
+      list.lock();
+      JX.DOM.alterClass(item, 'drag-sending', true);
+
+      var src_phid = JX.Stratcom.getData(src_list.getRootNode()).columnPHID;
+      var dst_phid = JX.Stratcom.getData(list.getRootNode()).columnPHID;
+
+      var item_phid = JX.Stratcom.getData(item).objectPHID;
+      var data = {
+        objectPHID: item_phid,
+        columnPHID: dst_phid,
+        order: this.getOrder()
+      };
+
+      var context = this._getDropContext(after_node);
+
+      if (context.afterPHID) {
+        data.afterPHID = context.afterPHID;
+      }
+
+      if (context.beforePHID) {
+        data.beforePHID = context.beforePHID;
+      }
+
+      if (context.headerKey) {
+        var properties = this.getHeaderTemplate(context.headerKey)
+          .getEditProperties();
+        data.header = JX.JSON.stringify(properties);
       }
 
       var visible_phids = [];
diff --git a/webroot/rsrc/js/application/projects/WorkboardColumn.js b/webroot/rsrc/js/application/projects/WorkboardColumn.js
--- a/webroot/rsrc/js/application/projects/WorkboardColumn.js
+++ b/webroot/rsrc/js/application/projects/WorkboardColumn.js
@@ -25,6 +25,7 @@
     this._headers = {};
     this._objects = [];
     this._naturalOrder = [];
+    this._dropEffects = [];
   },
 
   members: {
@@ -40,6 +41,7 @@
     _pointsContentNode: null,
     _dirty: true,
     _objects: null,
+    _dropEffects: null,
 
     getPHID: function() {
       return this._phid;
@@ -71,6 +73,15 @@
       return this;
     },
 
+    setDropEffects: function(effects) {
+      this._dropEffects = effects;
+      return this;
+    },
+
+    getDropEffects: function() {
+      return this._dropEffects;
+    },
+
     getPointsNode: function() {
       return this._pointsNode;
     },
diff --git a/webroot/rsrc/js/application/projects/WorkboardDropEffect.js b/webroot/rsrc/js/application/projects/WorkboardDropEffect.js
new file mode 100644
--- /dev/null
+++ b/webroot/rsrc/js/application/projects/WorkboardDropEffect.js
@@ -0,0 +1,35 @@
+/**
+ * @provides javelin-workboard-drop-effect
+ * @requires javelin-install
+ *           javelin-dom
+ * @javelin
+ */
+
+JX.install('WorkboardDropEffect', {
+
+  properties: {
+    icon: null,
+    color: null,
+    content: null
+  },
+
+  statics: {
+    newFromDictionary: function(map) {
+      return new JX.WorkboardDropEffect()
+        .setIcon(map.icon)
+        .setColor(map.color)
+        .setContent(JX.$H(map.content));
+    }
+  },
+
+  members: {
+    newNode: function() {
+      var icon = new JX.PHUIXIconView()
+        .setIcon(this.getIcon())
+        .setColor(this.getColor())
+        .getNode();
+
+      return JX.$N('li', {}, [icon, this.getContent()]);
+    }
+  }
+});
diff --git a/webroot/rsrc/js/application/projects/WorkboardHeaderTemplate.js b/webroot/rsrc/js/application/projects/WorkboardHeaderTemplate.js
--- a/webroot/rsrc/js/application/projects/WorkboardHeaderTemplate.js
+++ b/webroot/rsrc/js/application/projects/WorkboardHeaderTemplate.js
@@ -14,7 +14,8 @@
     template: null,
     order: null,
     vector: null,
-    editProperties: null
+    editProperties: null,
+    dropEffects: []
   },
 
   members: {
diff --git a/webroot/rsrc/js/application/projects/behavior-project-boards.js b/webroot/rsrc/js/application/projects/behavior-project-boards.js
--- a/webroot/rsrc/js/application/projects/behavior-project-boards.js
+++ b/webroot/rsrc/js/application/projects/behavior-project-boards.js
@@ -7,6 +7,7 @@
  *           javelin-stratcom
  *           javelin-workflow
  *           javelin-workboard-controller
+ *           javelin-workboard-drop-effect
  */
 
 JX.behavior('project-boards', function(config, statics) {
@@ -88,12 +89,24 @@
   }
 
   var ii;
-  var column_maps = config.columnMaps;
-  for (var column_phid in column_maps) {
-    var column = board.getColumn(column_phid);
-    var column_map = column_maps[column_phid];
-    for (ii = 0; ii < column_map.length; ii++) {
-      column.newCard(column_map[ii]);
+  var jj;
+  var effects;
+
+  for (ii = 0; ii < config.columnTemplates.length; ii++) {
+    var spec = config.columnTemplates[ii];
+
+    var column = board.getColumn(spec.columnPHID);
+
+    effects = [];
+    for (jj = 0; jj < spec.effects.length; jj++) {
+      effects.push(
+        JX.WorkboardDropEffect.newFromDictionary(
+          spec.effects[jj]));
+    }
+    column.setDropEffects(effects);
+
+    for (jj = 0; jj < spec.cardPHIDs.length; jj++) {
+      column.newCard(spec.cardPHIDs[jj]);
     }
   }
 
@@ -115,11 +128,19 @@
   for (ii = 0; ii < headers.length; ii++) {
     var header = headers[ii];
 
+    effects = [];
+    for (jj = 0; jj < header.effects.length; jj++) {
+      effects.push(
+        JX.WorkboardDropEffect.newFromDictionary(
+          header.effects[jj]));
+    }
+
     board.getHeaderTemplate(header.key)
       .setOrder(header.order)
       .setNodeHTMLTemplate(header.template)
       .setVector(header.vector)
-      .setEditProperties(header.editProperties);
+      .setEditProperties(header.editProperties)
+      .setDropEffects(effects);
   }
 
   var orders = config.orders;
diff --git a/webroot/rsrc/js/core/DraggableList.js b/webroot/rsrc/js/core/DraggableList.js
--- a/webroot/rsrc/js/core/DraggableList.js
+++ b/webroot/rsrc/js/core/DraggableList.js
@@ -45,7 +45,8 @@
     outerContainer: null,
     hasInfiniteHeight: false,
     compareOnMove: false,
-    compareOnReorder: false
+    compareOnReorder: false,
+    targetChangeHandler: null
   },
 
   members : {
@@ -53,6 +54,7 @@
     _dragging : null,
     _locked : 0,
     _target : null,
+    _lastTarget: null,
     _targets : null,
     _ghostHandler : null,
     _ghostNode : null,
@@ -372,6 +374,19 @@
       return this;
     },
 
+    _didChangeTarget: function(dst_list, dst_node) {
+      if (dst_node === this._lastTarget) {
+        return;
+      }
+
+      this._lastTarget = dst_node;
+
+      var handler = this.getTargetChangeHandler();
+      if (handler) {
+        handler(this, this._dragging, dst_list, dst_node);
+      }
+    },
+
     _setIsDropTarget: function(is_target) {
       var root = this.getRootNode();
       JX.DOM.alterClass(root, 'drag-target-list', is_target);
@@ -540,6 +555,8 @@
         }
       }
 
+      this._didChangeTarget(target_list, cur_target);
+
       this._updateAutoscroll(this._cursorPosition);
 
       var f = JX.$V(this._frame);
@@ -673,6 +690,8 @@
         group[ii]._clearTarget();
       }
 
+      this._didChangeTarget(null, null);
+
       JX.DOM.alterClass(dragging, 'drag-dragging', false);
       JX.Tooltip.unlock();