From reading rec.backcountry and following links, I picked up some valuable knowledge. We always camp near water (well, almost always), and I have yet to use soap to clean my dishes. It was pointed out to me that a bit of sand or mud in one's cookware works quite well. That's the method I use, and it doesn't leave soap anywhere it shouldn't be. In fact, I generally only use soap (Dr. Bronner's) once a day, if that (I carry baby wipes and pack them out), and a bit of toothpaste. The grit doesn't scratch my cookware, but it blurs the clear Lexan of the bowls a little. As small price to pay to not have to carry or use any more soap, and I've had no ill effects from this method.