If you havn't heard of or used iTunes U, you should give it a try.  A bunch of universities provide a lot of really cool information through lectures and question answer sessions etc.  Some of my favorite universities on iTunes U are Yale, Stanford, New York Law School, MIT, and UC Berkeley.  I found these are the best sources for information about business topics.  Some of the other schools seem to be promoting the school and don't give interesting business lectures like these schools.  Also you'll see a section on the iTunes U page in iTunes that says "Beyond Campus."  Under that section there is a link to the Gilder Lehrman Institute.  Here I found some facinating lectures on American Presidents and American History.  Be sure to check out the Lincoln and the Civil War Podcast.