I'm thinking of a tentative schedule for this season...
4/22/2012: PNC Park, Pittsburgh-- I could have started earlier, especially if I started with the O's here in Bmore. But I'm starting at home, because it's home and because it should have been Nick's 30th birthday.
Weekend of 4/27: Oriole Park at Camden Yards (oof, that's a mouthful of a name), Baltimore-- well, duh, I do live in Baltimore now, so I might as well knock it out early on. Especially because I've gone to an O's game in high summer before-- and NEVER AGAIN. OW, those seats were SO hot after baking in 106 degree heat.
Weekend of May 19: Nationals Park-- because DC is also, you know, right in my back yard. Well, kinda. Like 40-odd miles from my backyard, but still much closer than LA.
Weekend of June 23: Citizens Bank Park-- the next closest would probably be Philly. Doable as a day trip if a day game.
Weekend of July 21: Citi Field-- I think it's doable as a day trip for a Sunday day game
August: TBD Either Yankee Stadium (doable as a day trip if I can get Sunday day tickets) or Fenway (definitely will require at least an overnight stay) or Progressive (aka Cleveland, also requires an overnight stay).
September: Possibly Cleveland if it I don't go in August.