The Washington Post has an article on cask ales, those delicious beers typically served above 50 degrees Fahrenheit and carbonated only by natural conditioning. It's a good primer on what makes a cask beer different from beer served on standard taps.
I find cask beers much more flavorful that their carbonated counterparts.
In Durango, we're fortunate enough to have a few hand-pulled cask engines around town. Carver's always has its cask dedicated to Cascade Canyon IPA, a consistently solid bet. Durango Brewing Co. and Steamworks Brewing Co. also have casks, but in my experience, they aren't always in operation. Sadly, Ska is cask-less.