I image a Transitor and a Diode is going to come into play
Yep, one of each for each motor at least. And more stuff in you want other then just on/off control for the motors, like forward/off/reverse or bidirectional plus variable speed. Also you need to know the max current draw a each motor so you can see if you can power it from the arduino board (not likely probably) or you will need an external DC power source capable of supplying the total current demand of all the motors being on at the same time.
Lefty
