Mechanical engineering students from Delft University of Technology (Netherlands) have been working on Arduino based milling machine. As a base they took FisherTechnic building blocks and made skeleton for it.
Milling machine requires three stepper motors. Two of them are controlled using motor shield from Adafruit and third motor is driven by EasyDriver board from SparkFun. Arduino actually is playing simple part here – it accepts commands from Matlab using USB interface and drives motors. Not bad for one workweek project.