For some reason it took me a while to grasp the concept of allocative and productive efficiency. I finally got it because of this Jason Welker video. It goes through perfect competition, monopoly and monopolistic competition and shows it for each of them. If you want to see a quick replay go to the last minute of the video.
While I am on it Jason Welker teachers International Baccalaureate economics in Switzerland. His videos are longer than my 10 minute rule, but they can be broken into parts. His YouTube playlist is here and his website is here. Since IB economics has a component where students must relate the learning to the real world, Welker also has a blog which does just that. Below is a great tragedy of the commons story from Market Place which he just posted on his blog.