Mine are brand new so I haven't had to wash them yet. I think the idea of tossing them in the washer with some towels sounds pretty good. I have seen other posts where people cleaned them with Armor All or Simple Green. You could always just scrub them in the sink with some dish soap.
I tried hand soap and a wash cloth, and the dirt didn't budge(I where mine alot!), now that I know they can survive the washing machine, I am going to try that!