Here's a tip I picked up from Tony Vincent's magnificent
LearningInHand blog.
It's called
iQuiz and is available from Apple's iTunes store for 79p (yep that's right!) you can download the main iQuiz application which starts off as a music trivia game but then head off to
iQuizMaker.com and download the free (yes FREE!) iQuizMaker that let's you create your own quizzes for the iPod.
More info from Apple about iQuiz
here