I was there last weekend. I had both Shock Top and Red Hook ESB, which were on tap at the Chickie's and Pete's Crab Fries stand, plus a Miller Lite bottle from a vendor in the 300 section. I had been told there were Philadelphia Brewing Co. brews offered somewhere in the park, but after half an hour in the crab fries/beer line, I didn't take the time for a long search.

I'm guessing you're more likely to find a Brooklyn in Shea than in Yankee, but I could be wrong.

I would definitely drink Brooklyn if I was dumb enough to go in that stinkhole and they had it.

I've been to Oriole Park, Coors & Philly, and Oriole Park is far-and-away the best of the three for beer.
Oriole Park is the only one that I have seen that offers beers from all of the big three (A/B, Coors & Miller) while also carrying local microbrews, and classics like Stella Artois, Harp, and Guiness. Also, when you throw in the other beer stands at Oriole Park offering Natty Boh, Corona, and just about anything else you can imagine, their wide range of offerings can not be topped.
Coors field has the requisite Coors Banquet and Coors Light, and very little else. The only other offerings I found were Bud Light and Heineken. While the surrounding brewpubs / microbreweries like Wynkoop and Flying Dog help make up for it, the stadium itself is lacking in terms of variety.
Philly's new ballpark had a decent selection of the standard US beers and they did include a few microbrews. However, the microbrews were very limited in selection (one or two for a whole stand), so I was rather unimpressed. The best beer that I had there was some Yuengling Traditional Lager, which my hosts had special-ordered for their suite.

Rick

Dave - Good point about Philly's stadium - their lines are awful. I have never seen a stadium with concession lines as long and poorly designed as that one. Stashing away the only good beers in the park behind a line of 150 people is not the best way to go.

According to the Coors Field website there is Blue Moon Brewery in the park and their beers are available at a half dozen or so stands. Is this false advertising?

Does anyone know exactly where the Natty Boh Beer cart is at Camden yards? Last time I was there I asked several staff members and they had no idea what I was even talking about. Rick can you help?

Mark,
Coors owns and brews Blue Moon.

San Diego's stadium sells Karl Strauss beers. Good beer, good stadium.

Nothing compares to Camden though.

Natty Boh is in cans at Oriole Park. I found it in the "variety" stands on the lower concourse. Look for a beer stand where they have a range of different beers (Corona, and about 10 others) in a bin of ice in front of the workers. Granted, one can of Boh was about the same price as a 12-pack, but it was still nice to have.

I don't quite remember what I drank that night, probably something from Great Lakes Brewing, but a few years back I spent the weekend in Cleveland for a series against Cincy. I do remember that they served beer until the end of the game, which just so happened to last 13 innings.
Therefore, my vote is for Jacobs Field, a pretty ballpark, and I'm sure any Oriole fan would have to agree since it's nearly a twin of Camden Yards.

Philly got robbed. There are almost a dozen different PA-centric micros available in their park. It is by far the one with the best selection.
Baltimore--Aramark sold out to Heiny for the micro stands. They are green topped and you can get three different locals. The addition of Heiny cut back on the DuClaw porter, which was very tasty on warm days. On the club level, there is some McHenry and Sam Adams. If you are lucky enough to be in a box, they can hook you up with regular Sam Adams and their summer.
Coors Stadium--Coors brewing has one of their smaller pilot breweries there, the one that comes up with Blue Moon and others. They are owned by the big guys, but have a long leash. You can get some tasty brews there, but only if you have a ticket.