From the MAKE Flickr pool
Carl gives an old-fashioned marble a shot of electric oomph with this upgrade -
Arduino with motor shield controlling a continuous rotation servo. The wheel turns when marbles are detected by the infrared phototransistor and LED pair next to the wheel.
Full set here, includes Arduino source and demo video.
Neat – I’m guessing it would only take a bit more power and leverage to quickly turn this into an ‘outdoors only’ toy. Check out more project pics in the Flickr set.