From the 'Net: The Library of Congress' National Jukebox

The Library of Congress is our nation's testament to the arts: collections of books as old as our country itself and galleries packed with monuments in visual art. Now, they've provided the general public with easy access to their impressive collection of historic musical recordings. The jukebox brings together sounds recorded all over the world between 1900 and 1929, and each culture and musical style is represented. The Library's database is categorized for easy browsing, so it's easy to find yourself getting lost listening to the array of echoes from the past. My Irish heritage inevitably led me to two Irish reels recorded by Frank Quinn in 1920s New York City (also found a "humorous song" by Billy Murray in 1904 about the Irish). There's a treasure trove of interesting material available for free at http://www.loc.gov/jukebox/.