Hedger Wang has another great tutorial/demo. He’s created a dockable DHTML sidebar that allows the user to place it on any edge of the browser or leave it floating in the center of the screen.
I first thought about using this in navigation, but that may be a bit adventurous. It would be a great way to offer other site tools, such as your style-sheet changer, search bar, am I hot or not buttons, contact links, etc.