Instead of having the entire brains of the robot mounted on the body itself, you could try to shift the intelligence to a PC, and use RF or something to remotely control the movements of the robot. So the on-board microcontroller(s) will only have to acquire data from sensors, relay them to the computer via the RF module, and accept commands from the computer and drive the motors accordingly.

Alternatively you could have a reaaaaaally long serial cable and communicate between your uC and computer using Rs-232. Apart from length restrictions, its not as much fun as playing with radio ;-)

Basically you make your Robot a Remote-controlled toy, and put the control in the hands of your computer! :-) That way you can have more complex intelligence for your robot without having to use a more powerful microcontroller.

I have heard of some rather interesting digital radio modules (from TI I believe) that you can get as free samples. My friend has a few but is unable to use them as they are surface mounted... If you could obtain and use any of those, you wouldn't have to worry about the complexity of RF design and communication.

Kundi