Librivox has over 300 totally free audio books in the public domain. Volunteers read classic works by authors such as Mark Twain, Jane Austen, Dickens, Shakespeare, Tolstoy, etc., etc., etc.
Free audio recording of Thoreau's famous essay on Civil Disobedience. This essay is said to have been an influence on Ghandi and Martin Luther King. It's surprising how relevant much of the piece remains given the current political situation.