Kids! You CAN try this at home!
Well, you can if you have $50K burning a hole in your pocket. John Markoff in the NY Times - From PlayStation to Supercomputer for $50,000:

As perhaps the clearest evidence yet of the computing power of sophisticated but inexpensive video-game consoles, the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign has assembled a supercomputer from an army of Sony PlayStation 2's.

The resulting system, with components purchased at retail prices, cost a little more than $50,000. The center's researchers believe the system may be capable of a half trillion operations a second, well within the definition of supercomputer, although it may not rank among the world's 500 fastest supercomputers.

Perhaps the most striking aspect of the project, which uses the open source Linux operating system, is that the only hardware engineering involved was placing 70 of the individual game machines in a rack and plugging them together with a high-speed Hewlett-Packard network switch. The center's scientists bought 100 machines, but are holding 30 in reserve, possibly for high-resolution display application.

"It took a lot of time because you have to cut all of these things out of the plastic packaging," said Craig Steffen, a senior research scientist at the center, who is one of four scientists working part time on the project.

Here's the trick - they aren't using the PS processor, they're using the graphic chip:

The scientists are taking advantage of a standard component of the Sony video-game console that was originally intended to move and transform pixels rapidly on a television screen to produce lifelike graphics. The chip is not the PlayStation 2's MIPS microprocessor, but rather a graphics co-processor known as the Emotion Engine. That custom designed silicon chip is capable of producing up to 6.5 billion mathematical operations a second.

The impressive performance of the game machine, which has been on the market for a few years, underscores a radical shift that has taken place in the computing world since the end of the cold war in the late 1980's, according to the researchers.

While the most advanced computing technologies have historically been developed first for large corporate users and military contractors, increasingly the fastest computers are being developed for the consumer market and for products meant to be placed under Christmas trees.

Now I can build The Forbin Project in my basement!