You don't have to shampoo natural hair - try a co-wash instead!

Co-washing is simply using a conditioner to wash your hair instead of shampoo.  The harsh detergents in shampoos can often strip black natural hair of oils causing dryness and tangeling.  Since black hair tends to be dense it's not really needed to remove all of the oils to keep it from going limp. The conditioner combined with the agitation of your fingers will still remove odour, sweat, dirt and hair products.

Pick up your favorite non-expensive conditioner and wash your hair with that.  I used to like to use Aussie Moist conditioner.  You'll probably find that your hair will be softer and more moist than if you use shampoo.

On occasion use a shampoo to really kind of clarify your hair. For those of you that "grease" your scalp because it is dry/flakey co-washing may help reduce the scalp dryness thus stopping the need to "grease" your scalp.  I never did scalp "greasing"  it just caused my scalp to sweat and get stinky.  I think it used to help cause my face to break out too.  

However with my locks I do use shampoo. For a while I've been using Dr. Bronners Castille Soap.  It can be found in health stores.  I don't co-wash my locs because locs are basically strands of matted hair.  I do not really want to loosen my locs, however I condition with a traditional conditoner about once every 6 weeks to keep them healthy.  I use natural oils like Castor or olive oil to condition them about every second wash.