Adding a pair of brushed DC motors to a Raspberry Pi B+, A+, or Pi 2 is easy with this add-on board from Pololu. The board comes fully assembled, so all you need to do is connect it to a Pi as a HAT (Hardware Attached on Top)!
Two Freescale MC33926 motor drivers operate from 5 V to 28 V and can deliver a continuous 3 A per motor. (It can even run up to 5 A per channel for a few seconds.) The default pin mappings make it easy to get started using the provided software. But the board also exposes most of the driver chips’ I/O pins for more specialized applications. The PWM operation goes up to 20 kHz, allowing for quieter motor operation. It also includes a reverse battery protection circuit.
You can buy the Dual MC33926 Motor Driver for $34.95 from Pololu.