Fifty years ago at the Harvard Law School Forum, Dr. Martin Luther King Jr. gave a public address on the "Future of Integration." The audio of the speech is available on the forum's website; see here. (Hat Tip to HLS Communications)
The website--an absolute treasure--also contains audio recordings of addresses by many other historically significant figures. You can hear Barry Goldwater discuss "The First Hundred Days," (1961), Cesar Chavez consider “The New Grape Boycott — Will it Work in the Eighties?” (1985), Edwin Meese III lecture on “Freedom, Free Speech and the Courts” (1992) or Charlton Heston speak on “Winning the Cultural War” (1999). Other fascinating recordings feature panel discussions such as “Women – Dare We Not Discriminate?” (1966), which included Betty Friedan, Mary I. Bunting, and Pauli Murray. All told, the site is a terrific resource for researchers.