This question is somewhat similar to this: http://mathoverflow.net/questions/1714/best-online-math-videos
I'm using the word "history" loosely here. What I'm looking for are those lectures that put various mathematical developments in perspective by explaining their origins. There's something very insightful about seeing someone talk about the origins of a concept, that makes things click. Especially if he or she partook in the inception of that development.
So: where can I find such lectures online?