I moved to Philly three years ago and I have meet the most people through:
1. Manayunk Sport and Social and Philadelphia Sport and Social. They have darts, dodgeball, and other not so "sporty" sports, but they do also have football, basketball, and softball, plus numerous other events. They both have websites so you can see which one is best for you, or you can just join both like I did.
2. Not sure if you like animals, but I volunteer at the Philadelphia Animal Welfare Society. It's a very easy group to get started with, and I have meet the best people while helping animals. You can learn more about PAWS here:
www.phillypaws.org. You can PM me with any questions and I would be more than willing to help you!
3. Volunteering at my Pretzel Park, which happens to have a dog run, but is a nice park none the less. And I also hang out at Gorgas Park a lot--really cool community events there. Spring Into Your Park is April 26. Go to a park and get involved, you'll be sure to meet people.
You can also check out meetups.com. Never used it myself, but some people swear by it.
I hope my suggestions help. I really, really love living in Roxborough, and I hope you love Philly too.