The file /etc/security/console.perms should contain: <dri>=/dev/nvidia* /dev/3dfx* /dev/dri/* /dev/misc/agpgart instead of <dri>=/dev/nvidia* /dev/3dfx* to allow games like Quake3 to run as non-root on (say) Matrox cards.
This shouldn't be an issue anymore with udev, I think.