Cream of Nature, and it's cheap too
Beauty without cruelty makes several sulfate free shampoos. Drugstore.com carries most of them. These are pretty reasonable too.
Jessicurl has two sulfate free cleansers although they leave as much oil in my hair as they take out product. So that's great for dry hair but not so good for my virgin hair.
I've tried several from Aubrey Organics. My favorites so far are the Calaguala Fern Treatment Shampoo and the Egyptian Henna Shine Enhancing Shampoo. The product bottles do state that they are formulated for oily, fine hair (I have very fine but not oily hair), but I've never had a problem with dry hair as a result of using these shampoos (even in arid Colorado). I condition BEFORE shampooing to help prevent tangles, since I do notice more tangling occurs with these shampoos. Conditioning after shampooing makes my curls limp.
The Calaguala Fern Treatment Shampoo is protein-free and lathers much like a shampoo with sulfates, but the Egyptian Hanna Shine Enhancing Shampoo is low lathering. Another plus (IMO) is that all Aubrey products are free of paraben preservatives.