Dynamic Drag’n Drop With jQuery And PHP
http://www.webresourcesdepot.com/dynamic-dragn-drop-with-jquery-and-php/
HTML5 drag and drop in Firefox 3.5 – 0xDECAFBAD
http://decafbad.com/blog/2009/07/15/html5-drag-and-drop

Since it’s so fundamental, offering drag and drop in web applications has been a no-brainer ever since browsers first offered mouse events in DHTML. But, although mousedown, mousemove, and mouseup made it possible, the implementation has been limited to the bounds of the browser window. Additionally, since these events refer only to the object being dragged, there’s a challenge to find the subject of the drop when the interaction is completed.

Drag and drop is one of the most fundamental interactions afforded by graphical user interfaces. In one gesture, it allows users to pair the selection of an object with the execution of an action, often including a second object in the operation. It’s a simple yet powerful UI concept used to support copying, list reordering, deletion (ala the Trash / Recycle Bin), and even the creation of link relationships.