I've been PMing with Mat today and he asked me to post this here...
If you look at the top of the sidebar on my blog (
http://www.natarem.com), there's a collapsible menu. I only have two categories, but obviously any amount is possible. Also, things like the icons, colors, size, etc are all customizable. One option that I have turned off is the menu's ability to remember what you had open/closed the last time you visit the page. I assume 2+2 would want that turned on.
Anyway, Mat wanted feedback on that general type of collapsible menu.