There are several options...A Barley Crusher is what I have, it works, but only has one "driven" roller, the other is a floating roller so it tends to get jammed up some times....A MaltMill is what my LHBS uses/recommends..both rollers are "driven" so it tends not to jam.
But if you hook a power drill up to the Barley Crusher it works well...I ran 22lbs of grain through mine last brew day in about 10 minutes (I have a 3lb hopper).,