Sporcle is website of fun timed trivia challenges. Sporcle has become one of the most popular mentally stimulating diversions. If you have never played or heard of Sporcle...you might not want to check it out because it is very easy to get hooked :) Sporcle is particularly popular among college students.
Every now and then I will test my wits with some Sporcle games. It is frustrating that even when I think I do well, my score is sometimes poor compared to other Sporcle players. For example, on this recent quiz I only missed one! ...that still put me at only the 54th percentile though.