Calvin and/or Alex can probably fill you in more... but basically anything that has to do with politics, elections, congress and congressional rulings, blaming the current president for everything (in about a year it will be somebody else). Abortion and religion are also very hot button topics. All three causes hot tempers and 'passionate' debate that devolve into name calling sometimes.
I think there used to be a unique set of rules listed on the old site but the FAQ and rules here are the standard 'boilerplate' rules that Alex hasn't updated or added onto.
There's been threads on the topic of home improvement locked so really, it doesn't matter what the subject is. What counts is the fighting that occurs. It's one thing to express your opinion but when people start calling people names or the discussion never stops that it'll get locked.
But I wouldn't worry too much about it, as long as you're respectful you'll be fine.