Just need to make some motors move with your Arduino? Here's a simple way from SparkFun - the Ardumoto!
Arduino is supposed to be a convenient way to make things interact with the real world. But by itself, it can't move a motor. If your project needs you to make one or two DC motors spin, here's a straightforward shield from the guys at SparkFun: The Ardumoto!
This shield features a surface-mounted L298 H-bridge IC, which is a very well proven motor driver. It can control up to two DC motors bi-directionally, at up to 2 amperes per motor.
This is a motor shield for Arduino that will control two DC motors. Based on the surface-mount version of the L298 H-bridge, the Ardumoto can drive up to 2 amps per channel. Although the chip itself can take up to 46V input, this shield takes its power from the same Vin line as the Arduino board, and 46V will most likely cause the poor voltage regulator on the Arduino to die a sudden death. Keep it under 16V, and it should behave nicely.
The Ardumoto shield features:
Control for motor attached to OUT1/2 is connected to Arduino digital line 12 (direction A) and digital line 10 (PWM A).
Control for motor attached to OUT3/4 is connected to Arduino digital line 13 (direction B) and digital line 11 (PWM B).
Note: You might want to select a few connectors to finish the interface for your shield!