This rig or better this farm built by a member of overclock.net forums, has 51 graphics cards (NVIDIA 8800) on 13 MSI P6N Diamond motherboards. All the power is used for Folding at Home.
5 Rigs of 20 GPUs
3 Rigs of 12 GPUs
More pitures here: nitteo’s F@H GPU2 FARM.