I've tried various solutions to bring a mouse and keyboard to the PS3, but the most elegant idea I've seen by far is the mLani MoBi.
One part 2000DPI laser mouse, one part the left part of the PS3 controller, the MoBi essentially replaces the bulky mouse and keyboard setup with a mouse and half-gamepad setup. So alongside the perfect aim of a mouse, you get an analogue stick and D-pad for movement controls and weapon switching. While there's no price at the moment, the MoBi should be available this May.
Then again, I have a suspicion I've grown to prefer gamepads for console first person shooters only because drivers are bad on the PS3—even for so-called "supported" games. Do anyone else feel a certain indistinguishable disconnect when playing the PS3 with a mouse and keyboard? I actually score more frags in Unreal Tournament with my SIXAXIS. [Kotaku]