The Allegro SLA7062M stepper driver is a excellent choice for a versatile and robust stepper motor driver.
This device will let you drive a unipolar stepper motor at voltages up to 46 Volts and 3A per phase. It employs an internal PWM control of motor current which is can be set by a pair of external resistors.This is a microstepping driver capable of sixteenth-step operation which will make it possible for you to drive your motors very smoothly, almost as if they were DC motors.Unfortunately, the package has an awkward pin spacing that makes a PCB quite desireable. It is possible to bend the pins to fit 0.1″ matrix board, or they can be cropped and wires soldered directly. In the UK, you can buy this chip from Farnell.