diff -r 0b5da310ed15 src/order_gui.cpp
--- a/src/order_gui.cpp	Sat May 22 17:17:27 2010 +0200
+++ b/src/order_gui.cpp	Sat May 22 18:31:21 2010 +0200
@@ -459,6 +459,7 @@
 	};
 
 	int selected_order;
+	OrderID order_over;     ///< Order over which another order is dragged, INVALID_ORDER if none
 	OrderPlaceObjectState goto_type;
 	const Vehicle *vehicle; ///< Vehicle owning the orders being displayed and manipulated.
 
@@ -689,6 +690,7 @@
 		this->InitNested(desc, v->index);
 
 		this->selected_order = -1;
+		this->order_over = INVALID_ORDER;
 		this->owner = v->owner;
 
 		if (_settings_client.gui.quick_goto && v->owner == _local_company) {
@@ -949,6 +951,12 @@
 			/* Don't draw anything if it extends past the end of the window. */
 			if (!this->vscroll.IsVisible(i)) break;
 
+			if (i != this->selected_order && i == this->order_over) {
+				/* Highlight dragged order destination. */
+				uint top = (this->order_over < this->selected_order ? y : y + line_height);
+				GfxFillRect(r.left + WD_FRAMETEXT_LEFT, top - 1, r.right - WD_FRAMETEXT_RIGHT, top + 1, _colour_gradient[COLOUR_GREY][7]);
+			}
+
 			DrawOrderString(this->vehicle, order, i, y, i == this->selected_order, false, r.left + WD_FRAMETEXT_LEFT, middle, r.right - WD_FRAMETEXT_RIGHT);
 			y += line_height;
 
@@ -1184,6 +1192,12 @@
 		}
 
 		ResetObjectToPlace();
+
+		if (this->order_over != INVALID_ORDER) {
+			/* End of drag-and-drop, hide dragged order destination highlight. */
+			this->order_over = INVALID_ORDER;
+			this->SetWidgetDirty(ORDER_WIDGET_ORDER_LIST);
+		}
 	}
 
 	virtual EventState OnKeyPress(uint16 key, uint16 keycode)
@@ -1264,6 +1278,26 @@
 		}
 	}
 
+	virtual void OnMouseDrag(Point pt, int widget)
+	{
+		if (this->selected_order != -1 && widget == ORDER_WIDGET_ORDER_LIST) {
+			/* An order is dragged… */
+			OrderID from_order = this->OrderGetSel();
+			OrderID to_order = this->GetOrderFromPt(pt.y);
+			uint num_orders = this->vehicle->GetNumOrders();
+
+			if (from_order != INVALID_ORDER && from_order <= num_orders) {
+				if (to_order != INVALID_ORDER && to_order <= num_orders) { // …over an existing order.
+					this->order_over = to_order;
+					this->SetWidgetDirty(widget);
+				} else if (from_order != to_order && this->order_over != INVALID_ORDER) { // …outside of the order list.
+					this->order_over = INVALID_ORDER;
+					this->SetWidgetDirty(widget);
+				}
+			}
+		}
+	}
+
 	virtual void OnResize()
 	{
 		/* Update the scroll bar */