I've been seriously considering trying my hand at cold process soap making as well - as far as exfoliators go, I was considering a "morning scent" soap, and using some coffee grounds (that had already gone through my pot. For a couple reasons: one - don't want to waste coffee (LOL!) and two - having them go through the pot would soften them somewhat, making them gentler on your skin) as an exfoliator. I've read in a few places that coffee grounds have oils that are good for your skin - or maybe it's the caffeine in it ... does anyone know for sure?
I'm still gathering supplies, or I'd have tried it already, but I think it would smell awesome - coffee & maybe cinnamon? Have to be careful with cinnamon though, as it can burn sensitive skin ...