I've heard really good things about Dark Matter, as well as Afterglow. These are formulated specifically for just after you work out. They're a little on the spendy side, so if you want something cheaper, just go with straight whey protein, and a glass of juice. The juice will flush your body with carbs, and release insulin which will counteract your catabolic state, and the whey will flush your muscles with the protein you need to synthesize into lean mass.