Forums in general.

I'd just check them daily(ish) and participate in various conversations. These days this kind of communication is either in chat groups on Telegram or ephemeral threads on HN and reddit. Rarely are those threads referred back to, unlike topics were. I still do things online that last, such as blogging, pushing to Github and writing stackexchange answers, but none of those are very informal and include joking around sometimes, like we did on forums.