nvidia is the FreeBSD port of the nvidia graphics driver. It is found in /usr/ports/x11/nvidia-driver.
To activate the nvidia driver in X after installing this port, change the nv (or vesa, etc.) in the Device section to nvidia. You can also run X -configure to let xorg figure it out. You might want to add the DefaultDepth directive to the screen section, otherwise you will have only 256 colors.
To check compatibility of video cards, or for more detail:
- Hardware Configuration, Audio/Video
- "Hardware Notes" of the relevant FreeBSD version in http://www.freebsd.org/releases/