Sporcle
Millions of community-built trivia quizzes, playable free with ads.
Sporcle is a user-generated trivia platform — type-the-answer quizzes on everything from state capitals to one-hit wonders, timed and scored. The library is enormous and almost entirely community-submitted, so quality varies, but the geography and general-knowledge sections are consistently solid. Free to play; an ad-free membership exists but nothing is gated behind it.