So I went to the iTunes Music Store looking for a song which Patrick put on a mix tape for me over a decade ago. But I couldn't remember the name of the song except that it had to do with vampires, so I put "vampire" in the search box. That led me to a free vampire audiobook (in podcast form) called Forever Fifteen. In the "Listeners also subscribed to" box, there was another podcast called "Audiobooks with Annie," which provided readings of classics in the public domain. I was intrigued enough to visit her home page, where I found out about LibriVox, a community audiobook site, where every audiobook is released not just for free, but to the public domain. (Even Project Gutenberg's audiobooks are copyrighted.) Now, I see that there's a New York Times article about LibriVox. Well, let it be known that I knew about it before the Times did, then.
And now you know how.
edit: Patrick tells me in comments that the song in question was "Club Mekon" by the Mekons. (Now how could I forget that?) Alas, the iTMS doesn't seem to have it.