You can also get a motor driver that has controllers for all all 3 motors on one board.
I am currently building a 3D printer and got a complete kit that includes a very nice motor driver. Here is the link:
http://store.makerbot.com/electronics/assembled-electronics/reprap-motherboard-v1-2.html
You can buy one fully assembled or you can build your own. Everything is open source so all schematics etc. are available online.
http://www.reprap.org/bin/view/Main/Generation3Electronics
IT is used in the REPRAP http://objects.reprap.org/wiki/Mendel and the CupCake http://www.makerbot.com/ printers.