Peter Saint-André mentioned Thinkbot yesterday.
[Thinkbot] searches its database of registered users who, as with GlobeAlive, provide information about the topics on which they consider themselves experts (or at least knowledgeable). I don't really understand the emphasis on finding experts, when folks probably just want to find other people they can chat with about a topic in which they have an interest. But maybe that's just over the horizon...
Maybe I shouldn't have put 'experts' in the description. I only added it after seeing Globe Alive, and thought "so... if it's experts they want...". Then took it out again, then put it back in again. In fact, the experts thing is a side possibility of the system. My original entry - Proper P2P - had a better description of the original idea, which was that when you get to your computer (or mobile device, or whatever), you send Thinkbot the ideas that are on your mind and you want to talk about. Everyone does the same, making it easy to find people to discuss what's in your head.
I wish people would sign up to all these services right now (it's as simple as one IM message with Thinkbot). Once the possibility exists to do this, Googling seems so lonely.