Bill Gates has purchased the famous Feynman lectures on Physics and made them freely available to view on the Web. Available on Microsoft Research website called Project Tuva. The Microsoft Silverlight browser plug in is required to view the videos. The video player plug in was designed to make the viewing experience more interactive by allowing the viewer to search the lectures, take notes while you watch, and click on links to related content on the Web.
To learn more about this project, you can read the Microsoft press release here