It's Time To Test The Radeon/Intel/Nouveau Drivers
Once per Fedora release cycle they run graphics test days whereby they try to have users run a bleeding-edge Fedora Linux LiveCD on their hardware to see how the latest open-source graphics drivers are working out. Afterwards, feedback is requested to go on their Wiki.
Today is the F18 Nouveau test day, tomorrow is the F18 Radeon test day, and Thursday is the F18 Intel test day. Even if you don't active use Fedora as your Linux distribution of choice, testing is encouraged since it's a very easy LiveCD to use and the work of Fedora on drivers and other components usually ends back up upstream thanks to Red Hat's commitment to improving open-source.
Things to test come down to running the GNOME Shell or KDE4, DPMS power management, X-Video, RandR rotation, restarting the X Server, VT switching, suspend-and-resume, multi-head (where applicable) and then 3D/OpenGL tests like OpenArena and Tux Racer.
More details can be found out from this mailing list post.