I really enjoy using United Streaming. One of my favorite features of U.S. is that you can download segments of the videos which makes it easy to embed into PowerPoint presentations. I have used this frequently to liven up some otherwise boring PowerPoints. I also have used CNN student news, BrainPop and other streaming sites but I prefer the variety available on United Streaming. I have never used schooltube but I thought that videos like this one: http://www.schooltube.com/video/c574d63248584265a52f/Long%20Division would be helpful.
Another helpful sight mentioned in the 11 Tools blog is Drop Box. This is a site that allows you to store and share larger files like videos that you would have trouble sending via email but is more private than posting on YouTube. I have used this site before but as an administrator it was usually to have teachers share videos of their own teaching so that I could coach/give feedback. As a teacher I could see using this as a resource to share downloaded videos with other teachers/team members. With older elementary students, this could be used as a way for them to record and share both projects and video journals about their learning.
As far as Copyright, I learned that it is way more confusing than I originally thought. I think it is interesting that you are allowed to use your judgement to decide if using a copyrighted material is fair use or not. I thought this video was especially helpful. http://www.youtube.com/watch?v=g4rTfZOX-IM&feature=player_embedded for understanding copyright laws as they pertain to teachers.