I haven't seen any new beer additions at the ballpark lately. I'd really like to get Clipper City on board. We had a great time talking to their employees last year at the Zoo Brew and drinking the Loose Cannon. FYI--the Zoo Brew will be at National Zoo on 8/21 this year, if you want to partake of a lot of good beers in one place.
http://nationalzoo.si.edu/ActivitiesAndEvents/YoungProfessionals/AfterHours/