The etymology game. (Via Metafilter.) Ten multiple choice questions per game. Try to get a good score, but also learn some interesting info. Like, did you know the cheer "ole" comes from "Allah" and that "admiral" is based on "emir"?
Play more than once, because you'll probably improve your skills at figuring out the right answer. I think I got about 7 of the first 10, but then I got all 10 right the second time, not because I happened to know the answers, but because I got better at thinking about why one answer made more sense than another. (That's the classic multiple choice skill -- and you know how useful that is in life.)