• Collège de France : the most famous French scientific institution has free-access lectures all year long. Most of them are available online too (from Mathematics to Philosophy through Archeology).
• The MIT publishes a number of lectures in video-on-demand (and has a large web site named OpenCourseWare).
• OpenYale is presenting seven free introductory courses taught by distinguished teachers and scholars at Yale University.
• Courses of all levels from the Washington University (introductory, undergraduate, graduate).
• PodCasts from UC San Diego
• Lectures from Vanderbilt.
• Computer and Computer Graphics, from University of British Columbia or from Virginia U.
• Webcasts from Oxford Internet Institute.
• Webcasts from Rice University.
• Podcasts from York College (NYC).
• Harvard at Home.

I could also advise you to check the Lecturefox Blog with a lot of information about these free lectures.