...but I was working there.Here's the answer to your problem. Do things. Be active. You can find extracurriculars — dancing and yoga are wonderful activities, as are any sorts of gatherings that involve intellectual conversation of any sort — but the fastest, simplest, stupidest answer is that if you're active in things that require other people, you're getting out and meeting them and bonding with them.
On paper, I have perhaps the most antisocial set of interests you'll ever find. I spend hours and hours on the computer, I delight in writing essays and similar longform, I'm fascinated with both postmodern and classical literature, I listen to bizarre avante garde music. Essentially if you wrote up a list of things you weren't supposed to do if you wanted friends, I'd be everything there. And last year it was true: I didn't talk to many people, I spent hours in chat rooms, I tried not to leave my room.
This year I've changed that, and now I find myself going out several times a week purely socially, with several bunches of people with whom I'm also making things. The work simply gives us a reason to get together.
Curiously, I also find myself using Twitter and Facebook more and more as I become more social, because as I've stopped looking at them as tools of communication and started to use them more playfully, there's less inhibition involved.
Let me throw a twist in, however, because thus far I might as well be describing entrepreneurs, and entrepreneurs, while fun, may not be the sorts of people you want to get involved in. My twist is this: Find people who aren't anything like you. If you're a technologist, don't bud around with technologists. Find people with other talents. Take advantage of the fact that everybody's good at something, and let them take advantage of you. That way you're playing to your strengths but you're meeting different people who do things you're not familiar with. Then, if you want to shed the image of yourself as a geek who spends his time, say, writing five-paragraph responses late at night on Hacker News, learn about whatever all those other people know. Let them teach you things. It makes you well-rounded, it gives them the pleasure of talking about what they love, and it lets you exist without falling back on that geek crutch.