UChannel

UChannel is a consortium of universities that makes public affairs lectures available to a general audience by distributing free video and audio recordings in many digital formats - for streaming, downloading and broadcast. - http://en.wikipedia.org/wiki/UChannel

Website: http://uc.princeton.edu/main/

or just look up Youtube.com

A good example is http://www.youtube.com/watch?v=eOU9nQeoMww on energy security. It's about an hour long.