Self balancing robots have become very popular in recent years. BBot will be at the top of the heap soon since it is soon to have Bluetooth capability and be able to balance on a ball. Have a look at the robot here, and if you are interested in making your own you can buy all the parts needed here.

“The main objectives were:

* integrate the motor driver & controller
* aim for small size
* easy to manufacture (eg components on one side)
* optional daughterboard for standard university atmega/arm7/cyclone boards - takes over control
* onboard micros measure inertial sensors and calculate tilt
* able to take over motor control if daughterboard locks up/student enters dodgy control parameters
* aim for expandability - external port connectors and I2C bus header in case larger motor driver is needed, etc.”