This spring gets my only "A" rating so far. This is the best drinking water on the planet. They're not too keen on letting the public visit the actual spring, but you can get the water at your local supermarket.
Pictured here is the company headquarters on Center Street in Hot Springs, which you can visit, and where you can sample the company water. The building (a beautiful piece of historical renovation) is built on top of DeSoto spring, which is supposed to be pretty good water, too. Unfortunately, DeSoto spring has a flow rate of only about three gallons a minute, so they use it only within their own office building, recently for a hydroponics demonstration.
Mountain Valley Spring itself is several miles away on highway 7. The photos on this page are from the company brochure. The lower photo is of the springhouse.
Magical Waters | Arkansas Travelogue home page