There's the pretzel ride which happens on tuesdays, basically people gather at the art museum around 11ish and ride down this soft pretzel company who start rolling out the fresh ones at midnight. Delicious. I've only done it twice but I had fun both times. I believe critical mass is on Friday also? Never done it, but I think that's when it is.

Some fun bars/pubs/taverny things to check out:

700 club - my favorite bar, great beer selection, good dj's on the weekends no cover, upstairs dancefloor area has old furniture and wallpaper, feels like a house party

McGlinchy's - divey joint with sweet jukebox and surly waitress and you can still smoke in there if that's your thing. always a bunch of bikes out front.

Bob & Barbara's - $3 gets you a shot of jim beam and a pbr, can't beat that. they often have these 3 old dudes playing jazz, thursday nights they have a drag show if you're into that.

Tatooed Mom's - cheap food and cheap booze, just go there it's fun.

Standard Tap - Awesome food, only local craft brews on tap, cool atmosphere

Silk City - Used to be a diner with a small club attached (a GREAT diner at that, jesus I miss it), just got renovated and it looks pretty slick, decent food, dj's every night (Thursdays are big). I really miss the old, but it can be fun.

I could go on, but that's a pretty good start, ask around when you get here, (most) people in Philadelphia are a lot friendlier than the media portrays us.