I just discovered this website:
If you enjoy fascinating lectures, this site will make you happy. Registration is free, and from there you can download the talks in various formats. Here is a short excerpt from the “about” page:
TED stands for Technology, Entertainment, Design. It started out (in 1984) as a conference bringing together people from those three worlds. Since then its scope has become ever broader.
The annual conference now brings together the world’s most fascinating thinkers and doers, who are challenged to give the talk of their lives (in 18 minutes).
This site makes the best talks and performances from TED available to the public, for free. More than 100 talks from our archive are now available, with more added each week. These videos are released under a Creative Commons license, so they can be freely shared and reposted.