Foodery is closest if you are just staying downtown. Two locations.
As someone else posted, check phillytapfinder when you get there. They usually update the beers every few days.
If you are in the burbs, there's the Beer Store in Southampton, Capone's in Norristown, and Wegman's in Warrington. There are other, but those are the ones I go to for individual bottles.
Prices from low to high are usually Wegman's, Beer Store, and Capone's. Capone's blew me away with some of their prices. I think RR Damnation was $6.99 at Wegman's, $7.99 at Beer Store and $11 at Capone's.