I had one project in which I applied Walter Zorn's drag&drop library. It was used to enable users to drag around the toolboxes in a 'visual lay-out' CMS.
I intended to add support for dragging the content building blocks as well, Walter even modified the library to support dynamic adding of draggable elements, but unfortunately I never came around...
Dynamic adding means, that you not only can drag elements that exist already at the first time the web page has been called, but that you can add (via javascript) new elements (e.g. a new dhtml layer with a specific content, or a new 'iframe') -- and allow drag & drop for these as well.
Walter's lib can be found at:
http://www.walterzorn.com/dragdrop/dragdrop_e.htm
Best,
Fridolin
