Best areas for nightlife in Philly?

There are some cool speakeasys: The Franklin Mortgage & Investment Co., The Ranstead Room, and Hop Sing Laundromat (this last one has a dress code so make sure you're looking nice otherwise the owner won't let you in)

Manayunk (actually in Philadelphia city limits but not in Center City) and West Chester (Pennsylvania) (suburban county seat of Chester County) have a ton of great bars and restaurants.  In Center City Philadelphia, the area just east of Broad and south of Market, also has a ton of nightclubs and traditional bars.