Ask HN: Teaching online?

I've been around for a while and I've learned a bit about a lot of things, and a lot about a few things (e.g. programming, compilers, math, etc.) I'm looking for other (better?) ways to share what I've learned online and, in turn, better ways to learn. Of course, I'm aware of many ways to share: Wikipedia, blogging, math/stackoverflow, HN, various forums and email lists, etc., but none are quite what I'm looking for. In particular, I'd like something where I connect with people directly who have a problem or content they are trying to understand where I have expertise, the scope is not too small so you have a chance to build a relationship, and there is an ongoing dialog. Perhaps the closest is math/stackoverflow, but even there, I find many of the questions superficial and most questions have less of a back-and-forth/dialog than I would like. Ideas?