Lots of things are possible with stepper motors.
Are you planning on using some type of motor shield? (almost mandatory for unipolar motors)
Are you planning on connecting transistors/MOSFETs to the Arduino pins? (works just fine for bipolar motors)
Are you planning on using some type of driver board? (only 2 outputs from the Arduino - Step & Direction)
Are you wanting to go for some time, or some distance?
How fast do you want to turn?
One speed or several speeds?
How long does it need to run?
Do you need it to return to some starting point?
here's some code I was working on for a stepper driver - the function for the motor will work either as an interrupt function or as a called function - http://arduino.cc/forum/index.php/topic,84809.0.html