Two Graphics Cards?

I think i've seen somewhere that you can connect two graphics cards together to work in parallel. Dramatically increase your graphics capabilities, or something.

Is there truth in this? If so, any good articles? Links? How-To's?

And today's cards power is more than enough. If you want more, don't get two 6600s, get one 6800. By the time the 6800 is not enough, you don't want another 6800 for more brute power. You want a new card which implements the new shader models and effects.

SLI is useless. Just there to catch lusers.