To answer your questions: There's some ported games from Windows to Linux. Such as HALO. You can download HALO for Linux and play it on your PS3. Also,
Wine HQ gives .exe support for Linux. This means you can play .exe games on your PS3! Hurray!
Also, if you have any projects to do such as a 'rainbow table' or so, you can use the PS3's power to make a fast rainbow table graphic generator.
The PS3 is expensive for a gaming console, but cheap or a super computer.