I'm planning to build a simple XY plotter, and have been looking at the possibility of using a pair of small 5V 4-phase steppers to provide the movement. In my research, I've often seen stepper driver boards advertised, ranging from very big and expensive, through to quite small and cheap. Some of them actually look like little more than a darlington array on a PCB.
Do I really need one of those external driver boards, or can I control the steppers directly from my Arduino?