I saw a link on BoingBoing today about free documentaries on Google video. This got me started looking for kid-friendly science videos. Finding them in all of the clutter is hard, but there are some interesting resources available for free. If you have ever done the "oobleck" activity (i.e., cornstarch and water), you may want to check out some of the demonstrations available. (The link is for a "corn starch water" search. You may want to try other search terms as well.) Several videos, including one showing here, demonstrate vibration of the solution, creating some fascinating results.
There is so much that can be learned from such a simple solution, you should use extend "oobleck" lessons as much as possible. If you are looking for good lesson plans around oobleck, there are many out there. Two of the best are in Afterschool Science PLUS (review / link) and Great Explorations in Math and Science.