last updated: 2023-12-23
ed. note: this wiki post / page does not follow its own advice
a curated list
As of 2024, for the best reach, you should post to most of these, and set up some way to make sure you see replies, and then reply to the replies.
There are also lively discussion forums elsewhere: Discord, Signal, Telegram, Slack, various Discourse instances, etc. These are niches, not general public forums, but still valuable places to find your people and conversations.
Note that using each service or federation carries some political / social baggage / "correctness". Do your own research, ask your friends and desired social contacts for their thoughts. Some questions to consider: who owns them? who controls them? what's their business model? who do they let post even though perhaps they shouldn't? who do they effectively censor (explicitly or implicitly) even though perhaps they shouldn't?
Not listed above / ask me more about: Nostr, Ghost, Flickr, Threads.
Some reading: