There was recent discussion here about the song.
The Real Audio clip of the NPR segment on Tom Dooley is here.
Page with first recording of Tom Dooley and links to stories.
You can listen to The Smothers Brothers sing it (and talk a lot at first) at this page - which loads automatically, and can scare the whatsit out of you if you aren't expecting it. Warning for the humor impaired: Do not click on this last link - it's not a serious rendition of the song! ("Poor boy, you're hung...")