Using video in learning and teaching proved to be an effective activity in many disciplines. You can record your own videos or use the  ones done by others. YouTube, Khan Academy, and TED might be among the most popular ones used by students and faculty.

But there are more video resources available! Please browse http://www.freetech4teachers.com/2010/09/47-alternatives-to-using-youtube-in.html#.Umop0_mnqfA and see what fits the best for your teaching style, subject area, student learning style, etc. Happy viewing!