I noticed that Chris posted a while back about the use of an Arduino in an R/C car. I've haven't posted anything here about my project as it's not autonomous, doesn't fly, and isn't really a drone.
It does, however, borrow code from the ArduIMU for the sensor fusion so perhaps someone may find it interesting. "Normal" r/c motorcycles (yes, they do exist and are far more popular in Europe) use a loose spring linkage between the steering servo and the forks. This allows the geometry of the bike to do the balancing and the servo can just nudge the bike to lean to one side (using counter steering.)
My solution uses a more rigid servo connection driven by the output of a PID control. The operator's steering input, the IMU's roll angle output, and the forward velocity of the bike are used to compute the steering angle to hopefully maintain balance while providing steering control. Works well on road - real objective is for off road though.