I would nix the softsoap, since most soaps are actually chemically rather different than detergents and tend to leave residue.

What I generally use (and, in fact, use for doing hand laundry at home, too) is shampoo. It's typically a bit more diluted than liquid detergents, but that is not a huge problem.

The other product I like is Dr. Bronner's Magic Soap, which is usable as soap, shampoo, detergent, toothpaste, and provides hours of reading entertainment on the label.