There is a free application for Windows Vista and Windows 7 which implements the exposé functionality found in Mac OSX or a Compiz enabled Linux distro, and it does it very well. It’s called Switcher.
If you have Vista or 7, I strongly suggest you try Switcher out. It’s smooth, responsive, and extremely tweakable. It works good on dual monitors too.
Credit to criccio for the video.
You can download it here http://insentient.net/