I love it when teachers and their students share the work they are doing. One terrific example is MathTrain.TV. Mathtrain.TV is a free, educational "kids teaching kids" project from Mr. Marcos & his Students at Lincoln Middle School in Santa Monica, CA. Here's a sample project.
You can read more about this project in the article entitled Move Over, Sal Khan: Sixth-Graders Create Their Own Math Videos. To learn more about the genesis of this project, take a look at this video.
If you are interested in trying this yourself, you can view some screencasts about how to make screencasts on the MathTrain.TV site. Some of the resources are free, while others must be purchased. Sources referenced include: