I found this little tracked robot platform at mutr.co.uk. It's quite difficult to find tracked robot platforms (or even the components) cheaply, but this is very nice for the ~ ten pounds they charge. It contains the tracks, wheels, motors and gearboxes, an aluminium plate for the chassis, fixing screws and some three-way switches and wire. It needs a bit more than just assembly to get it moving - I had to fold and drill the aluminium and glue some of the wheels together, and I found the motor tended to rise out of the gearbox if I didn't tie it down with some copper wire.
Somewhere I have some infra-red proximity sensors and a camera board I'd like to attach to it to make it into a proper robot. It'll need a suitable battery and some motor controllers - the Electronize controllers I have at the moment are a bit too big for it.
MUTR sell a lot of useful stuff - I got some Nitinol memory wire at the same time, which is very interesting stuff. Their £5.80 default delivery charge is a bit annoying for small orders, but handily I have some colleagues who also buy from there to share costs with.
