[6600gt]

Put a range finder on a servo and ever certain incriments record the value to create a map of the area around you.
What type of microcontroller are you going to use? The 18f series pics inside the RC would work just fine. You can order a sample pack of the microchip website for free. These are more work to get started with but they are far more power full then then the Basic Stamp and cheaper. In fact you can get the processing power of the RC.

If you want to use cameras you need far more powerful controllers, possibly a laptop on the RC car.
I wanted to build something like this too but haven't had time. Though I have been playing around with PICs.

Look at the Mars Rovers. They use black and white cameras, for navigation, which are probably much easier and faster to process.