You can use Arduino. These gadgets are quite good and not very expensive, I have seen pretty clever hack projects using them (GPS, Lego Mind Storms, webserver, etc.)

http://en.wikipedia.org/wiki/Arduino

I think you can use an arduino board as the interface between the car and the netbook. Also, they are quite good and you could even make the robot with the arduino itself (they have modules for Bluetooth and Ethernet. I would imagine that they also have a wifi one).