The two acronyms I know of in the area are:
) which meets in Phillly and Glenside, PA
EPGS which Ed already linked to, which meets up at the Oxford Valley Mall in Bristol or Langhorne, PA, whatever it is.
I've not been to PAGE, as their hours aren't convenient for me...
However, I can vouch for EPGS. They meet on the first and third saturday of the month from 10am until 9pm in the community room, hidden upstairs and down a back passage that sits opposite Sears amongst a clutter of kiddie rides, at the aforementioned Oxford Valley Mall. They do have yearly dues (first times free, kids.) Group composition is maybe half wargamers to half boardgamers. There are some serious Euro gamers, and you may find yourself stuck in the position of choosing between playing a Euro or sitting out of a game if you don't want to play (and it could be a while before another game ends). Its a good opportunity to play longer games (2-4 hrs) that might be difficult/impossible to play on an ATF night (Le Havre, for instance.)