Gigabyte have released a motherboard with four 16x PCI-Express slots, as well as two PCIe 1x slots. This means that by plugging in another graphics card to one of the slower slots, it's possible to connect 10 displays, giving you a desktop resolution of 6400×2048. I'm not sure whether you'd be able to play HL2 on one of these, but it would rock if you could. They managed to get it working with only a 480W PSU.

Source: Tom's Hardware