Read about Metisse just yesterday. A new approach to fancy/3D-Desktops by Mandriva. Unlike compiz, metisse has features that let you actually use windows in transformed status. Mandriva has some videos that show you some of the features.

As you may already have expected, I couldn't wait to create some ebuilds, so fetch my overlay (which is still called xgl, but don't care about that) for fancy x stuff and run emerge metisse:
svn co https://svn.hboeck.de/xgl-overlay

At the moment it requires it's own X-Server (very much like luminocity or xgl in the past), the window and composite manager is a modified variant of fvwm. After installing, run Xmetisse :1 on one console and on another one metisse-start-fvwm -wd :1. You'll get a fancy new desktop inside a window.

At the moment it very much looks like a design study, not really intuitive to use, but it has some interesting approaches. Nice to see that the linux desktop is evolving. For all non-gentooers, Mandriva has a live CD for you.