I used to go wilderness camping and spend up to 21 days in the Boundary Waters of Minnesota. We always carried the solar shower along with biodegradable soaps for the body, hair and dishes. I'm lucky enough to have an REI just up the road and in their store they have a rather large selection of different soaps that are safe to use.
My favorite brand is Dr. Bronner because it's organic, biodegradable, a little goes a long way and can be used for everything. It comes in pepperment (tingly), eucaliptis, almond and lavendar. Smells great.
http://www.rei.com/search?query=dr+bronner
Campsuds is another brand but i've never personally used it. I saw one that you didn't have to rinse off but I think I'd go baby wipes before I used something like that (me personally).
Burt's Bees also makes an outdoor bio soap and I've been thinking of getting that one next.
I just picked up Cabela's shower shelter too ~ it's on sale and hard to pass up. Comes with a solar shower. I bought it mostly for a changing tent to put next to the tear but in a pinch, I may use the shower.
Sandy