I been recently helping out adding improvement patches to Gentoo's distribution via the Xeffects overlay.
Gentoo is a great Linux OS which is source based. Gentoo supports managing and creating an overlay which allows you to customize individual packages.
What does this mean? Well, when people are testing modifications and improvements to things like KDE, X, etc, you can take these patch files and make an overlay to test them one Gentoo as well.
Xeffects is such an overlay, and contains fixes to KDE, as well as other desktop improvements for Gentoo (like Beryl).
Beryl is a Revolutionary way to look at your desktop and shows exactly what Linux can achieve, which is far beyond anything Vista has to offer.
Beryl is an branch of Compiz, which was originally developed as a proof of concept by Novel. The source was released to the public, and it has developed beyond a simple proof of concent into a full blown replacement window manager.