Bestest Best shampoo EVER: Kerastase Chroma Reflection Bain Mirroir 1
Well, any Kerastase shampoo is great really. Once you're on it, you're hooked and its hard to go back.
This particular one is designed for colored hair, giving it some extra shine and maintaining the color. A bit on the pricey side (~ $32 a bottle), but if you only use about a dime of it every time you use it (no need for more...unless you're rockin' a fro), the bottle can easily last up to 2 months.
I won't go on like a commercial, but get a sample of it and try it. It definitely kicks Herbals Essences, Pantene (except their conditionner), Tresemme and Garnier's asses. Combined.
Some other Kerastase shampoos are designed to condition damaged hair (from say bleaching or constant heat exposure), night time treatments etc.
But the result is always the same: cuddly, soft , healthy, awesome hair :D