Forums regarding controversial issues like gameplay etiquette, gender in chess, what is considered cheating, etc... Those tend to be rather heated.
There are also some really informative forums that rock - like forums talking about the best opening lines for the English, Daily Puzzle discussions, endgame strategy, post-mortem gameplay analysis...
All good topics.
There are forum that are hot but I don't know how to figure them out. I don't know whats hot and whats not. Can you please tell me? Don't be afraid!