A couple of weeks ago I got sick of the whole propritary/binary Nvidia graphics drivers. So I searched around for the best ATI chip that 3D graphics drivers in Xorg X11. I bought a ATI Radeon 9200. The 3-D driver is a bit buggy, but no worse than any binary drivers I've used. And I can hope that support for this card does nothing but improve.
Of course the only games I have that take advantage of 3-d on linux are Quake 3 and RtCW.