Just one, and she wasn't really a therapist. She was my hs guidance counselor... it took a long time to switch roles in my head, but we have been friends for about 15 years now. More like a mentor/mentee relationship, but we call it a friendship.
I don't think I could be friends with any of my other therapists. It's too weird a change in dynamic... I'm OK with the "contrived" nature of therapy. I'm not able to talk about a lot of the stuff I bring up in therapy with anyone else. There were things I talked about with my guidance counselor when she was in that role that we have not spoken of since... it's not that I wouldn't love to have someone in my life I could talk to about it, it's just how the relationship changed (and the heaviness of the stuff)...