There's Pennsylvanians for Medical Marijuana: Pennsylvanians For Medical Marijuana
Phillynorml.org
There's also a NORML group forming in Pittsburgh:

If you or anybody you know are interested in helping me found and maintain a legitimate Chapter of NORML in Pittsburgh, PA please post something here or contact me on Myspace: email search [email protected] or search my Myspace URL: myspace.com/bent_perception....., send a friend request and a message w/ your friend request so that I will aknowledge your friend request.... my profile is currently set to private as to ward off unwanted traffic! I look forward to hearing from anybody serious and passionate about the cause to help Legalize Cannabis/Hemp for Medical/Indeustrial/and possible recreational use!!!!