Hitting the jaunty-changes mailing list this afternoon is an automated message that the Nouveau driver named xserver-xorg-video-nouveau (version: 0.0.10~git+20081028+cea05e1-1) has been accepted into Ubuntu 9.04. This is good news for those not interested in using the obfuscated and feature-limited xf86-video-nv driver or NVIDIA's proprietary Linux driver.
Also exciting us are Jaunty updates for Mesa (a Git snapshot as of today), RandR 1.3, and many other updated X.Org pieces. More information on the xserver-xorg-video-nouveau driver for Ubuntu 9.04 can be found on its package page. It doesn't appear that Nouveau will replace xf86-video-nv as the default on new installations, so users will still need to manually make the move.