I’m one of two admins on wandering.shop; we were started as a friendly place for those interested in Science Fiction and Fantasy, and still have a large concentration of authors, but we’re open to everyone and have quite a lot of technologically-minded folk.
I think Patrick McKenzie is considered something of an expert on businesses of this type, and I find his blog/site Kalzumeus tremendously helpful. Following his twitter @patio11 is pretty good too.
I wrote ContactOtter, a shareable contact manager with logging. I think of it like a “family CRM”.
Closed beta right now, but I’ll basically approve anyone who signs up.
Right now you have to manually enter info, but it’ll soon have some auto-importing, tracking your social networks for connections (totally optional, I don’t want to be evil), and hopefully a mobile app in the next couple months.