I’ve previously used DOM-Drag, a similar library by Aaron Boodman, to create user interfaces that allow users to set the order of items by dragging them relative to each other. Aaron recently updated DOM-Drag’s documentation to include even more examples.
I prefer DOM-Drag’s API over Drag & Drop’s as it uses smart object orientation to provide hooks for performing additional actions when drag related events occur. Drag & Drop’s API is less flexible but the library provides resizing support out of the box and has compatibility with older browsers. I recommend trying out both before picking one as a starting point for your own scripts.
Walter’s site has some other interesting CSS experiments, including an impressive graph generator and a library for dynamically rendering vector graphics.