I am actually using a GeForce 2 MX 400 that works great! My WB Desktop is set to 1280x1024 @ 32 bits (and 100Hz refresh rate, which is due to the combination between the monitor's maximum allowed refresh rate and that provided by the card). At present the GeForce 2 is the best supported card. I also heard about the GeForce3 and 4 but you'll need Gary's kernels for those to work.
Regards.