The one crucial place to hit is Kraynicks, in Garfield ({link}) - it's like via bicycle in Philly, but four floors and a fourth of the price - lots of NOS and general OS, lots of weirdness. The bad news is the hours - it's closed Wednesday, and is open 11:30 - 6 (I think) on Tuesdays, so if that strikes your fancy, plan accordingly.

Also, if you have your (fixed) bike, there is a 6/6/07 "neighbor of the beast" alleycat - see http://myspace.com/pghbikeracing