Well I'll be here all summer. Just don't expect me to know anything about the city.
Leo, where you at in Philly? I lived there for 4 years, so I and a wealth of knowledge on random shit to do there.
Good bars in Philly:
Monk's Cafe - 16th and Spruce - Excellent selection of Belgian beers, traditional Belgian food
Eulogy - 2nd and Chestnut - Excellent beer selection, but not as stuffy as Monk's
McGillins Old Ale House- Located in an alley between Juniper and Broad south of Chestnut
Of course, you need to answer the most important question in Philly. Pat's or Geno's? Both at the intersection of 9th/Passyunk. I suggest you get one from each and split them. Personally I prefer Pat's. It's all about the Amoroso bread.
Museums
Philadelphia Museum of Art - End of Ben Franklin Pkwy - Worth it, if only to climb the Rocky steps
Mutter Museum - 22nd between Chestnut and Market - Amazing collection of the freaky side of medical history.
South St between 2nd and 7th is always entertaining. Lots of just random shit, and plenty of freak watching.
I'd also recommend making the 1.5 hr trip to Atlantic City, but since you just came from Vegas, you would be disappointed.