I think muscle milk is the best bang for buck, plus it's the highest protien per serving. Only 2 small scoops, and it tastes great. But, others have had great success with whey protien.
Beverly International can't be touched. More whey hydrolysates than any other. Not to mention Muscle Provider tastes so good you forget it is a protein shake. No lie, McDonald's could sell it as their chocolate shake.