How do you find someone who has seemingly disappeared?

Someone very close to me has been on my mind alot lately and I dont know how to contact him. I've tried all the usual methods such as Facebook , MySpace, and the typical Google search but have found nothing. I don't even know if he is dead or alive. It would be nice to know either way. I last saw him in 2007 and he looked like hell. We tried to stay in touch but for some reason his number changed and he vanished again. Does anyone know of a way I can try to find someone? What options do I have? I feel pretty damn helpless.