Its based on the Atmel Mega644P MCU and has an dual H-Bridge driving two geared motors with Quadrature Encoders on them. I first wrote (ok found other examples on the web and then made them better) interrupt drivers to update two sined long integers holding the movements (forwards and back) at 564 ticks per 1 revolution of the motors (Faulhaber).
It also has an MicroSD card for recording the movements to fat32 file system for later playback.
It also uses a P.I.D. routine for very smooth movements.
Its actualy a board I built similar to one on sparfun.com. If its the processor board your wondering about, its a Mega644P I wired myself.
I later rebuilt it on a PCB.
I'm now currently working on a new board that has an xBee interface, MicroSD socket and more. This board is being built in cooperation with Eddy from wrighthobbies.net and will be for sales some time soon.
There is another board that goes with this that has a USB controller and a socket for an xBee wireless device. The realy cool feature that this has is the abuility to remotely upload new code wirelessly and then talk to the controller via USB/seria!