One environmental note of warning: never discard soapy water into or use soap in a stream or lake. Instead, wash yourself and your pots away from the water and rinse away from the water too. I have found that a good swim in a creek or lake will clean the body fairly well without the use of soap. All that soap does, anyway, is to dissolve grease, and there is only a small amount of skin oil on our bodies.
Source : Ken Kifer's Bike Page : Tips and Tricks for Bicycle Touring / Photo from Bike Nerd.