National Jukebox
The Library of Congress presents the National Jukebox, which makes historical sound recordings available to the public free of charge. The Jukebox includes recordings from the extraordinary collections of the Library of Congress Packard Campus for Audio Visual Conservation and other contributing libraries and archives.
vinfille: My grandmother had whole boxes of piano music from her mother's era, with references to Enrico Caruso and the like. It's fascinating to be able to hear some of these past-famous singers- I had no idea they had even been recorded.  
spoon: real cool