I'm thinking about entering Pi Wars in December. It's a Raspberry Pi based robot competition.
So far, I've scrounged a few bits and pieces, and put together a really basic remote control system using a Playstation 3 controller, an L293 H-Bridge driver board and an Arduino. The Raspberry Pi can do PWM and USB/Bluetooth, so it can take the place of both the laptop and the Arduino, when I get that far.
There are a few bugs, as I mention in the video, related to input handling. Basically if I play with it too much, the motor gets stuck (usually at maximum speed) and I appear to stop getting events from the joystick char device. But for now, here's a short video.