HN is useful for this too. My particular niche is that I'm an academic researcher, but I think there's a bunch of stuff that's poorly presented in academic papers, or at least only presented in a way that's intended to be read by other people in the same field (or sub-field, or sub-sub-field). So one of my medium-term plans is to re-present some of the stuff I like in a less jargony and formal way, in tutorials / blog posts / whatever. But often that gets pushed off behind other obligations, and it feels like Work, even if it's work that I enjoy. But posting an explanation of something I know about that comes up in a discussion on HN just feels like conversation, much more natural. It's not always as polished as a result, but sometimes I've actually used my HN comments as a first-draft of a longer tutorial.

For example (for a bit of self-promotion), this recent comment possibly could've been a better-written and better-edited blog post, with some images and examples, and a title like "implicit and explicit models in interactive fiction", or I dunno, something like that but catchier: http://news.ycombinator.com/item?id=2177226. But writing something like that would probably sit on the TODO list for a long time; meanwhile I just banged out that comment in 20 minutes or so because it came up in discussion. The fact that it was "replying to a comment" rather than "writing a thing" somehow tricked it into not feeling like writing. Now if I ever want to write a blog post, I have a draft of the idea written out.