Finally had to give in and get a motorshield for the Arduino. I purchased it from RobotShop not knowing that it was a kit (i.e. you build it yourself). I should have read the title of the item a little better. It was fun to build the shield with these instructions PDF. It helped me build up some soldering skills. Fortunately, I bought some soldering flux paste from Radio Shack which helped me keep my work clean. The shield lets me power up to 4 DC motors, 2 servos or 2 stepper motors. You can use it to power bigger motors using an external power supply. The shield has 4 H-Bridges provided by L293D chipset.

I set it up with a RC car which has 2 motors for steering and forward/reverse movement.

All the instruction on how to build the motorshield and how to use it with the library are available on this ladyada.net website