I know this is an old discussion, but I'm well-versed in this subject. I've usually got 4 or 5 hobbies going at a time.
I agree with the suggestion about photography. I'm not normally much of an outdoorsy person, so it's great because it gives me a reason to get outside more. And I've gotten into some interesting discussions when I run into other photographers. I actually met a boyfriend once because he came up and started talking to me about my old Minolta I had with me.
Also knitting is a good one. It's nice for when you just want to relax at home, or you can take it out with you to a park or a coffeeshop or what have you. I sell at craft shows every so often and you meet a ton of cool interesting people that way.