If you are looking for a motor driver then heres a good one:
http://www.solarbotics.com/products/k_cmd/
it can drive 2 motors at 6 to 50V, at up to 4A total output current. It is a nice little kit that delivers nice current for its price. It also has an onboard voltage regulator so its the perfect thing to connect between you batteries, arduino, and motors ;D