I'm a big drinker. I have to carry water on any run over 1/2 an hour.

For shorter runs I have an Amphipod 4 bottle belt. I like it because I can put water in some bottles and sports drink in others. The belt is stretchy so it conforms to my body and doesn't bounce around

For the longer runs I have an Innov-8 fanny pack. It's got a bladder and hose set up like a Camelbak. I put 2 Amphipod bottles on it for sports drinks. I like this pack because the bladder is oriented horizontally. It distributes the weight around you, so it rides without bouncing.