A few years ago I went gluten free, and tried a few of the beers available at the time. Unfortunately, none of them were satisfying to my palate. Thankfully I'm not gluten intolerant, so I opted to stick with real beer.
A truly gluten free beer is not made with barley or wheat. The main ingredient is usually sorghum. They tend not to taste like barley based beers.
A few years ago, an enzyme was found, that when added to beer prior to fermentation, dissolved the protein bonds that holds the gluten together. In the specific tests to determine what gluten levels are, the FDA states that anything below 40 ppm can be stated as "gluten free", beers made with this enzyme test at below 10ppm.
Omission is one brand that should be available nation wide. New Belgium just announced two beers that will be made with this process. My (Station 26 Brewing Co) Colorado Cream Ale is made with this enzyme. If you wish to stay away from barley and wheat, New Planet out of Boulder makes a true gluten free beer.