This short guide will describe how to use nVidia's drivers to create an OpenGL accelerated desktop environment similar to AIGLX. Currently, driver revision 9631 or higher is required for stable releases of Compiz and Beryl.
Should be the latest guide for getting xgl and compiz working on ubuntu - didn't work for me because I'm running Ubuntu 6.06LTS and some packages weren't available (beryl and emerald)