Okay, I really need to stop posting so many google talk videos. But I know most people do not have the inclination to watch the hours and hours of lectures from google to find the good ones.
Philip Zimbardo give an amazing talk about Evil and how good people can be made to do evil things. If you know a ton about psychology this might not be new but this talk really blew my mind. If you have any interest in the human condition this is totally worth a listen.