How to find long-lost people?

So, I'm trying to track down this long-lost (for various complicated reasons) cousin of mine, Tina Thakar, who I know married a Michael Vaulter and settled down in San Francisco before we really lost track of her. I noticed that she was on classmates.com and laid down $40, but the email address they have must no longer be valid. There isn't anything promising in any of the online phone books. Anybody know of other ways of tracking people down? (Then again, maybe she doesn't want to be found...)