I would suggest the easiest and fastest route to your goal would be an Easydriver board board available from Sparkfun. It is for small motors (.75A per coil) but it is well documented on various sites. Sparkfun also sells a small motor that works well with it. A larger motor would require a driver with more capacity like some inexpensive ones by Pololu. The Playground section of this site has plenty of info to get you started.