A hacker who goes by the name madshaun1984 has figured out how to successfully get XBMC to run on a PS3 unleashing its media streaming capabilities.
Right now the CellSDK that this hack uses isn't finished, but the hope is to turn the PS3 into a proper media-streaming Linux box. He highly recommends that you don't update the firmware.
For full instructions on how to do this, you can go here.