Does anyone know of a good debate website?

I particularly enjoy discussing politics, history, economics, etc. But I really don't like the format on Yahoo! Answers; for the most part (at least what I've seen) people see a question, comment, and then leave. No real debate takes place, and it leaves my desire to school people bleakly unfulfilled.

Obviously I prefer if it is free, a fairly easy format to learn how to use and popular enough so that a discussion can take place in the timeframe of an hour if everyone participating wants it to be. Any help is greatly appreciated!
I have tried Experience Project as well, but not nearly enough people for each topic I am interested in, and people seem to be very touchy to having their ideas attacked from what I've seen.