TED.com is one of my favorite websites. TED stands for Technology, Entertainment and Design. There are TED conferences hosted all over the world. The idea behind TED is to invite the greatest minds of the current age to a stage and have them give a 20 minute or less talk on a topic they are passionate about.
While some of the videos are mind-numbingly complex and/or boring, most of the ones I've watched have been nothing short of fascinating, motivational, thought-provoking, mind-bending, thought-altering and absolutely worth the 20 minutes it takes to watch one.
If you are in the field of education and are not watching some of these videos, I would strongly recommend that you give them a try. Most are absolutely usable in a classroom. Some will be more appropriate for older kids, but there are certainly videos on here that will appeal to elementary and middle school-aged students.
Give it a try and let me know what you find.