Public Domain MP3s: Robert Johnson, Et. Al.

Believe it or not, I made this discovery while undertaking legitimate research in the workplace.  To demonstrate some techniques around making Flash and XML communicate, a programmer showed on his blog how he created a simple MP3 player ... and he used as source material some music found at PublicDomain4U.  There is some great stuff there, playable online or downloadable, from the likes of (some of my favorites) Robert Johnson, Blind Lemon Jefferson, Louis Armstrong, and many others.  Some samples above, in my own player.