Available for free here (note: a new Microsoft plugin is apparently required):

http://research.microsoft.com/apps/tools/tuva/index.html

What a wonderful, wonderful thing! They are the Messenger series of lectures from which Feynman's book "The Character of Physical Law" was made. One of my favourite (of many) things from that great man. So Gates does another of his noble gestures for Humankind. I don't know how to feel about that guy sometimes...

If they weren't locked into Microsoft's closed, proprietary, non-standard formats, I might be a little less grouchy about this than is actually the case.

(Quick edit - to be fair, Flash isn't much more open / Free / libre.)

I completely agree!

Thanks nprev for pointing out the lecture series. I have watched the first four lectures and they are great. Other than the shuttle hearings, I had never heard him speak and it is great to hear his New Jersy accent (maybe NY). I was a freshman in college--a physics major--when these lectures were taped. I have enjoyed several of Feynman's books, and watching these tapes is really fantastic.

[edit] Watched all seven lectures. The lectures are for a general audience, but when you knnow some physics, you really appreciate how welll he explains difficult concepts. Wow.