For talks with quizzes and questions and lessons you can customize. See TED, Ideas worth spreadingopens in a new window.
For free, K-12 educational videos, check out WatchKnowLearn.com.opens in a new window There are over 33,000+ indexed videos, that are organized, reviewed, and rated.
Learn almost anything for free at Khan Academyopens in a new window. This website offers educational videos on almost everything.