Smart Bitcoin Investments Forum - dead forum.
BTC Reddit/Bitcoin Reddit - just links to bitcoin section on reddit, anyone can find it easily by yourself.
Bitcoin Talk - I guess it's suppose to be link to bitcointalk, but such links not working here.
Bitcoin Forum - similar to this forum, have some users and activity, not much, but alive at least.
Bitcoin.com Forum - same as Bitcoin Forum, but with interesting design, not like other crypto forums, modern.