The standard A4988 stepper motor driver from Pololu is an excellent design, and is hugely popular in the DIY community (especially in 3D printers). Pololu saw that they could improve on the standard design by making it exactly the same, but on a better circuit board that dissipates the heat better, so you can have more power out of exactly the same electronics.

Specifications:

• Proven Allegro A4988 Stepper Motor IC
• Simple and proven “Step” and “Direction” control method
• High-temperature thermal shutdown, undervoltage lockout and crossover current protection
• Built-in short protection
• 8-35VDC input
• 4-layer, 2oz copper PCB for improved heat dissipation
• 1.2A continuous current per phase (no heatsink nor airflow cooling)
• 2.0A continuous current per phase (with adequate heat-sinking/cooling)
• 3-5.5V logic input
• full, 1/2, 1/4, 1/8, and 1/16 microstepping modes
• header pins included, but not installed