Adafruit Motor/Stepper/Servo Shield for Arduino kit - v1.0

Here is a design for a full-featured motor shield that will be able to power many simple to medium-complexity projects.

• 2 connections for 5V 'hobby' servos connected to the Arduino's high-resolution dedicated timer - no jitter!
• 4 H-Bridges: L293D chipset provides 0.6A per bridge (1.2A peak) with thermal shutdown protection, internal kickback protection diodes. Can run motors on 4.5VDC to 25VDC.
  
• Up to 4 bi-directional DC motors with individual 8-bit speed selection (so, about 0.5% resolution)
• Up to 2 stepper motors (unipolar or bipolar) with single coil, double coil or interleaved stepping.
  
• Pull down resistors keep motors disabled during power-up
• Big terminal block connectors to easily hook up wires (18-26AWG) and power
• Arduino reset button brought up top
• 2-pin terminal block and jumper to connect external power, for separate logic/motor supplies
• Tested compatible with Arduino Mega 1280 & 2560, Diecimila, Duemilanove, and UNO
• Download the easy-to-use Arduino software library, check out the examples and you're ready to go!

Kit comes with all parts necessary, unassembled. Instructions, examples, and other documentation is available on the website
Motors and Arduino are not included.

Details:

• Dimensions(assembled): 69mm x 53mm x 14.3mm (2.7in x 2.1in x 0.6in)
• Weight: 32g / 1.15oz

Motorshield Tutorial:

• FAQ
• Make it!
• Use it!

More resources:

• Wikipedia has tons of information on steppers
• Making things' tutorial on steppers
• Jones on stepper motor types
• Jason on reverse engineering the stepper wire pinouts