EVGA has released a Website where it shows you what Tri SLI can do. EVGA also claims that with the help of a 3 SLI bridge that you can buy from a company you can make the Tri Sli in existing EVGA 680i motherboards. The 3-way SLI bridge is selling at EVGA's Website for $19.99 and it is currently available.
All you need are three e-GeForce 8800Ultra 768MB, or alternatively three e-GeForce 8800GTX 768MB, and it should rock and roll.
EVGA and Nvidia claim that you will get 25 FPS with three cards in Crysis DX10 settings with three cards, below 20 FPS with two cards and only 10 FPS with a single card. Well, it is an interesting marchitecture but it costs a hell of a lot of money.
You can check it out here.