MSY Archives:Community portal
The most recent community, and by far the most active. Mostly a place for general discussion and fun with people who like To the Stars, rather than for discussion about the story itself.
(To get an invite use the Reddit link above - you should get one within 24 hours.)
This is the oldest available source of discussion and speculation for To the Stars, running since early 2013. The most in-depth discussion still largely takes place here.
A more recent community hub, for those who prefer subreddits to forum threads.
More of a community project than an actual community, it's still a very filled-out list of employed tropes.
Hieroynm posts all fanart to his Tumblr. This is a collection of all posts there tagged as such.