I've found that as I started corresponding more in the "real world," email took hold as the most important tool I have. When I was a student, less so, because all I used it for was holding passwords, subscribing to a list or two, and occasionally communicating with a teacher. All my friends were always nearby so it wasn't a major issue to just hang out all the time.

But since then, everyone I know has moved somewhere else. If you want to seek out a deep long-term conversation and you can't get in physical proximity to do so, email does that quite well.

I think mailing lists are a powerful tool as well - they should probably be used more. I hate using Facebook, even though it's valuable as a Rolodex replacement.