Due to the nature of small group reading instruction, I have limited opportunities to use video streaming with students. However, I have utilized YouTube on a variety of occasions to plan and present a variety of staff development presentations. Below are introductory videos on earthquakes and pioneer life. I might share these with my students prior to reading a book on the subject. These can be helpful to build background knowledge prior to reading.
I found the copyright videos very informative, and I'd be lying if I said I didn't learn a few things. I never knew there was a parameter on Google Images that finds images available for reuse! I will also be sure to look at some of the other sites mentioned instead of defaulting to using Grab from now on.
I've had a Dropbox account for the last 2 years, and it has become a valuable resource for document sharing across a group of teachers who are hundreds of miles apart.