Hullo! I don't know of any clubs or groups, but no one has posted anything and I didn't want the disscussion to get upset because no one commented on it! Maybe someday there will be a PA Nerfighter club, and someone will reply to you, disscussion; have hope! DFTBA!
There are countless of organizations based in Philadelhpia. None that I know of that are actually just for 'fighting worldsuck,' which DOES suck, but hey, you should start one.
What you should do is decide what kind of volunteer work you want to do, and then seek out a club for that. That kind of club is more likely to exist within easy driving distance. So, do you want to work with animals? Fight slavery? Work with homeless youth? Paint Murals for peace? Or do you want a more international organization, like a Humane Society base in Philly or a Red Cross base in Philly? Free the Slaves probably doesn't have a Philadelphia base because, despite being an international organization, they are pretty unknown. Which isn't good. You could help them out, though - they're always looking for volunteers that are going to take initiative and start organizations in different cities and towns.