TeacherTube, the YouTube for teachers is the showplace for teachers to display their original instructional movies. It is worth spending time looking through the library of movies, as you can find some real gems. But, beware, like YouTube in many ways, "Garbage in, Garbage out!"
Note: Once you find a movie you wish to use, either embed the Source Code, or convert the file in Zamzar so you can easily use it in your multimedia presentations.