i just installed opensolaris 052008. I found this nforce driver for my gigabyte mb : http://www.nvidia.com/object/linux_nforce_1.23.html
for video : http://www.nvidia.com/object/unix.html
My configuration : NVIDIA GeForce 7100 / nForce 630i Chipset
--> For nforce driver, i don't know how to install it.
There is also these : http://homepage2.nifty.com/mrym3/taiyodo/eng/
--> nforce 2/3/4 and mcp61
tell me if it works for you
bye, good luck