you could check out traders laboratory, trade2win as well as the broker-specific forums (eg IB has a forum, TD ameritrade and etrade have forums, etc).
Here's another one, I would say the second best after ET. It doesn't have frequent messages but the archive is big and all threads are very focused and straight to the point: https://www.interactivebrokers.com/smf/index.php?board=2.0