From the guys who brought you Samurize comes Cairo, a new Desktop Shell Replacement for Microsoft Windows.
The goal with Cairo is to "transform your desktop from the dated Windows user-interface to a brand new system that will change the way you use your computer forever." Pretty ambitious stuff, but looking at the concept work and screenshots they've released so far, it's at least going to be a damn pretty custom shell!
Cairo is rapidly approaching Milestone 1, and they've selected their first batch of testers. Keep an eye on this project though as it looks very promising. Hopefully it'll be easy to skin...