The screen shot I have below is of Discovery Streaming. This online video resource has thousands of video clips in every subject matter imaginable. The clips are in documentary, cartoon, movie, and many more formats. I use Discovery Streaming for instruction purposed to enhance the unit we are working on. I use it for all subject areas, not just one. Sometimes students go to the computer lab and find their own videos in a particular subject matter and choose their own video to watch.
Podcasts and other audio tools can also be valuable tools in the classroom. I have tried podcasts before and elementary kids don't stay focused long enough without the video. However, adding Itunes and copyright allowed podcast to presentations can enhance them greatly. Although I have heard very good poscasts, in my opinion, video streaming is a great way to go with elementary and younger, but podcasting has its values for upper grades.