Bimmerfest & Rennlist... But I don't find them anywhere near as interesting as this forum and there's not much camaraderie (if any at all). Admins are too discretionary, and you need a minimum # of posts to do this or that. Good info, but I don't comb thru them often.
I’ve been part of Wrangler forums, Tacoma forums, Dodge Challenger forums and Fiat 124 Spider forums.
I enjoyed the Wrangler and Challenger forums the most: they have a good diversity of members, people are passionate and usually respectful of each other.
Members of the Fiat Spider forum are passionate and respectful too, but it doesn’t really have many members. So it can go dead for days at a time.
The Tacoma forums are weird: it has a very large number of members and tons of posts, but the discussions get nasty regularly. They have this ongoing thing called “Dumpster Fire Friday” by which members post the weirdest, nastiest things. A small group members posts inside jokes they think are “funny” but most members don’t get. The moderators are very hands off and allow all kinds of weird sh*t fly.