PS2 crunches data well
This nifty article from news.com discusses how researchers hooked up 70 PS2 game consoles, installed Linux, and made a supercomputer capable of a half trillion operations a second.
Turns out it's the emotion engine (their fancy graphics processor) that does a good portion of the magic.
Apparently it takes a rocket scientist to install Linux on the Xbox, which is partially why PS2's were chosen.
(oh yeah, and they have 30 more PS2's they want to link up for an amazing video display from the 70 box supercomputer)