You need to meet new people, try new things.
Is there something you always wanted to try, but never got around to it? Now is the time to do it. In order to meet new people you need to make yourself available for someone new.
Do something wild. Do something intense. Hire a personal trainer. Join the gay wrestling club in Chicago, even if you never wrestled before. see: http://www.wrestlechicago.com/info.html
Sign up for a fun course: foreign language, cooking, acting, trapeze, ballroom dancing, ancient Roman architecture; something you always wanted to learn but were never required to.
Get involved with a gay (or straight) political group. Join Human Rights Campaign and promote gay rights. Join Amnesty International and help free prisoners of conscience. Is there some issue you feel passionate about? Consider working for a political candidate.
Make the conscious decision to move on, and take a risk to meet new people.
If you are not capable of moving on at this time, consider therapy; many people overcome problems after getting some professional help.