Google Groups is, for whatever reason, the de-facto standard community website in the formal methods community. A group chatroom for low-stakes pseudo-realtime discussion A mailing list or forum for announcements & effortful discussions requiring multi-paragraph posts & responses; this should have an optional email interface A Q&A website similar to StackOverflow where the correct answer can be marked and elevated instead of staying buried in a long discussion Easy search function for all of the above, without having to create an account Certainly self-hosted FOSS communities can die, but these are functions of community activity itself rather than the service they’re hosted on.