It's been over four years since I wrote this blog entry on iTunesU, and the free lectures available there from a growing number of institutions, from Stanford to Yale. Professor David Blight's 27 lectures on "The Civil War and Reconstruction, 1845-1877" remains one of the exceptional educational offerings on the site.
Naturally, in the intervening years, there has been a veritable digital explosion of online material presented at no cost. This may explain why pioneers like The Teaching Company are offering some of their packages at greatly reduced discounts [incidentally, I was given the set of Gary Gallagher lectures as a gift, and you can't go wrong with that product].
More recently, I happened upon this nifty collection of 15 video and audio pieces from the National Portrait Gallery, ranging in length from a 4-minute snippet to an 85-minute lecture by James McPherson. It's really nicely done, all in the spirit of commemorating the 150th anniversary.
Two thumbs up. You can access all of this material, and much, much more through the iTunesU page of the iTunes store, or through this handy smartphone app.