https://www.phantasytour.com is one of my favorites. Phish in particular has a very vibrant community, if you enjoy their music you can find lots of other people who are passionate about them on just about any social network. For people who are easily offended there is also a forum on phish.net that prefers to avoid hostile conversations. Phantasy Tour has a lot of obscene discussions that most people would find offensive but is tolerated on this forum.