rollover pup-up menus

I have an idea for how I want to make the bulk of my desktop, but before I go about trying to figure out a new program, I thought I'd see if what I wanted already existed, or if it was really easy to explain properly.

I'd like to make a menu for the sides and top/bottom of the screen, which is just the title or whatever, then on scrollover comes up with a stretchably sized menu with text or icons in it, and the menu shrinks back when you take your mouse away from it. I was also thinking that clicking on the menu title would toggle the menu staying up.

It seems simple enough, and I figured out some of it already, but any help or pointing to what this sounds like would be appreciated.