Two professors from George Mason University provide this course in developmental economics at no cost to you. They divide their courses into chapters, each consisting of several videos lasting between 2 and 15 minutes. So far, there are also courses in international trade, classical economics, the Euro, the American financial system, the economics of the media, the economics of the USSR and the economics of Mexico.
You can find their website here.
Here is their first video for the developmental economics course.