If its smaller motors that you want to control, you need variable speed, or more options, and the motors are around 1A (Peak) or smaller, I would recommend a motor shield. I personally use the "Adafruit Motor/Stepper/Servo Shield for Arduino kit - v1.0"
Its about $20 for the unassembled one and is also a great way to learn about basic soldering.
Here's the link: https://www.adafruit.com/products/81
Although I have not tried it yet, but LadyAda suggest for more amperage, to stack L293Ds pin to pin. My L298Ns have the heatsink flange for all kinds of cooling tricks