It is unusual for gaming consoles to allow foreign operating systems to be installed on them. Since consoles are usually sold at a loss, they are usually locked down to prevent games from running on them without the publisher paying royalties to the console developer. Sony decided to open up the PS3 console a little bit, and allow third-party operating systems to be installed, with the caveat that they do not get accelerated graphics.
Because of this, you can now install Linux on the PS3. You have to jump through a few hoops, but it definitely works. Terra Soft Solutions has developed Yellow Dog Linux 5 in cooperation with Sony specifically for the PS3. It even offers, uniquely among distributions so far, support for those using it on PS3. Yellow Dog Linux (also known as YDL) has been an exclusively PowerPC-based distribution since its inception, so it was not surprising that Sony contracted it to develop the next version of YDL specifically for the PS3.