Hm, if your inability to socialize is as bad as you're saying it is, you might want to go to a psychologist, if only to see what they have to say. They'll probably have helpful advice on what you can do and give you some perspective. They probably have had other clients with similar problems, and can relay thier experience to you. If you are attending a university they might have a counseling center that offers free or low-cost sessions with professionals.
Random personal advice:
1) In conversations, Ask lots of questions. Questions make you sound interested and engaged (even if you aren't). "Oh, what's that?" and "So then what happened?" and the like can get you far.
2) Talk about your interest less than you want to do. I used to go on and on about what I liked for way to long because I didn't understand how much the other person really cared (much less than I did). I had to learn to catch myself from getting too technical or long winded- the lesson is to keep it simple, and keep it short, but don't hide it.
3) Do some research. You don't have to read books, just know something about them. Read the Wikipedia article on
Twilight, for example, as it's the big new thing, especially among girls. Use Wikipedia like Cliff notes for pop culture. Someone mentions movie X or singer Y? Google that shit.
4) This one's hard... find a friend who shares your interests but is more "normal" (for lack of a better word). Having a friend who knows how to act with most people but who understands how you are different is a big help, because they can form a sort of bridge between you and everybody else. You can learn how to socialize from them without feeling totally out of place.