Everyone is familiar with youtube and the material that can be found there. As school districts block more and more sites, the options for teachers becomes more limited. Teachertube is geared for educators and students and many of the videos are posted by other teachers.
This is a great collection of videos done by teachers on numerous topics. You can also upload your own videos to share with others. This has several applications.
This website has a lot of different videos, pictures, audio. etc that could be used in the classroom. All you have to do is type in what you want to search, and you will be amazed with what comes up! For example, I typed in "The Water Cycle" and had 10 different videos pop up!