What are some good sites that have online quizzes?

Someone just emailed me a quiz from some educational site, about government, philosophy, etc. You answered all the questions, it gave you your score and showed you the correct answers to the ones you got wrong. It told you the average score amongst college professors and the general population. It was fun and I would like some more sites that have similar quizzes.

Do you know of any sites that have quizzes?