As my introductory text was looking a little sad and lonely I've added a demo of my upcoming QuickMenu (working title) JQuery plugin currently in development. It's part of the new Silver Pride Content Management System and is designed to allow you navigate smoothly through many levels of heirarchical data. This isn't an original idea of course. I originally saw a similar implementation on this website. There were one or two things I didn't like about this version though, one of which was the dependancy on Ajax calls to another page. I therefore decided to write my own compact version. I took some inspiration from http://www.deviantart.com/ categories list.
It's fully accessible and should degrade nicely (i.e. still work) if Javascript is disabled as it builds a menu from a simple html list. Also, I've implemented JQuery animations where taste allows to give a nice IPOD style sliding menu effect.
When I get a chance I'll refactor the code and explain how everything works so that others can use it. But in the meantime, here is a simple demo.
http://aob.silver-pride.com/quickmenu/quickmenu.htm