I have scavenged quite a few unipolar stepper motors from copying machines over the years. Some of them are quite big (and heavy).
I also desoldered the stepper drivers asociated whit the motors. Mostly STK6713 type chopper-drivers.
I would really love to put this stuff to use, and not spend $$$ on bipolar steppers and drivers, just to be able to do 1/4 and 1/8 stepping?

How does 1/4 and 1/8 stepping work anyways and what's the benefit?
Can I wire my 6-wire unipolar steppers for bipolar operation?
What are the benefits of bipolar compared to unipolar?