Check out Sierra Club outings in your area - you don't have to be a member to go, generally, and you can meet a lot of people who might want to hike with you on trips NOT organized by the Sierra Club. It's a great way to socialize with others interested in backpacking. Haven't done any SC hikes in quite a while, but I enjoyed the ones I did go on. Some leaders are more fun than others, you can get a feel for which ones you want to keep hiking with. You might even decide to become a leader yourself, if you enjoy the social aspects of backpacking as you say.

http://www.indiana.sierraclub.org/groups.html