Quite impressive is the list of the available lectures and interviews, that span from Architecture to Politics, even if the great majority of them are related to Computer Science in general (almost 1.400 when other categories at present only include a few dozens of videos) and in particular to Artificial Intelligence, Machine Learning, Semantic Web and Data and Text Mining.
Conferences of distinguished international personalities can be seen, including lectures and/or interviews of Umberto Eco, Noam Chomsky, Eric Schmidt (Google CEO) and Tim Berners Lee.
I gave a quick glance to a couple of Semantic Web related lectures that seem quite interesting. Especially this very complete Introduction to the Semantic Web, taken at the ISWC 2008 in Karlsruhe, Germany, deserves to be mentioned, since it provides a quite detailed explanation (9 parts for about 5 hours and half overall!) of the basics of this technology plus an analysis of the state of the art at present.