The folks over at pabr.org have figured out how to get the PS3 SixAxis controller to work in Linux – in Bluetooth mode! In USB mode, the controller is a standard USB HID device, so it works fine as a basic controller in Linux already. But when Bluetooth is used, you get to make full use of the motion-sensing capabilities of the SixAxis. This opens up many possibilities for use with things other than games. (not that there are any games that make good use of this ability – on the PS3 or otherwise).
Check out this demo video showing just how responsive the SixAxis is – it is really cool to see it controlling something tangible like that.