Just found this while reading the Makezine blog:
The Arduino grblShield is a complete hardware solution for Dank's CNC motion control system called grbl. Compatible with the Uno, Duemilanove and Mega versions of the Arduino development platform.
- 2.5 Amps per winding
- 12-30 Input Voltage
- Open Pin Pass Through
- 8x Microstepping
- Screw Down Terminal Voltage Input Hardware
- 3x Axis (x,y,z)
- 3x Robust TI DRV8811 Stepper Drivers
Find it Here
While I would like to develop my own, this seems like a good value.