One of the cooler games that launched with the original iPod was music quiz. It did something interesting (albeit a little under-developed) by making you guess which song you were listening to in an attempt to see how well you knew your music library. In that same spirit of using content that's already there is PopJax, a trivia game that uses Web media and user-created questions to entertain. It started out as a Facebook app, but has launched as a standalone site this morning.
The quizzes on the site are designed entirely by users. Most are multiple-choice, but creators can pick true-or-false and fill-in-the-blank questions, too. After each question is created it goes into a pool for other users to view and vote on. The cream of the crop gets added into each genre of game feed that plays a little bit like "Jeopardy," with point values for each question answered correctly. There are also variations of the board with a simple 3x3 grid, and two 4-in-a-row modes; one that plays like baseball (too many strikes and you're out), and another that plays like a slot machine with random questions that spin into place.
The one weak point of the service is your connection and the legal status of the content. Sometimes videos are slow to load, and if a video is taken offline (which tends to happen with movie and music clips) it's your job to alert the system. Other than that I found it to be an enjoyable distraction and one of the few sites to graduate from Facebook into a destination of its own.