commercial&non dhtml menus   (link)

http://www.dynamicdrive.com/dynamicindex1/
some of these are user-submitted... not sure of licensing terms, didn't poke around much yet

http://www.opencube.com/
http://dhtml-menu.com/

http://www.google.com/search?hl=en&ie=UTF-8&q=%22dhtml+menu%22&btnG=Google+Search

and non-commercial ones:
http://simplythebest.net/scripts/DHTML_scripts/dhtml_script_105.html