Blackface Then and Now - Greil Marcus

A March 2008 hour-long+ lecture from U.C. Berkeley. From the description:

"Somebody has to black hisself / For somebody else to stay white." So wrote Melvin B. Tolson in the 1930s in A Gallery of Harlem Portraits. Though we may think of blackface performance as a relic of the past ("I saw one of the last blackface minstrel shows," Bob Dylan writes of his boyhood in Hibbing, Minnesota, in the early fifties), cultural critic Greil Marcus will take up the persistence of blackface in contemporary culture, as bad conscience, yearning dream, and indecipherable joke.

If you're not a fan of watching lengthy videos on your computer (I'm not), the U.C. Berkeley site has the audio available as a downloadable podcast. There are also various tools available to download YouTube videos and convert them into a format that can be watched on a video iPod.