I am a long time fan of the Internet Archive, a nonprofit organization dedicated to preserving all human knowledge in its various forms for future generations. One amazing effort of theirs is The Great 78 Project.
The Internet Archive has gotten hold of thousands of vintage 78rpm discs, a precursor to the vinyl record, made of a much more fragile resin. By digitizing and making available the original recordings, the Archive is ensuring that people everywhere can access these works of art from prior eras, even after the originals deteriorate beyond the ability to play them.
Already there are more than 25,000 recordings available on the Archive, including lots of swinging numbers, many novelty recordings, and historic audio documents like political speeches. Note that the archivists captured the discs as is, with plenty of imperfections, hisses, pops and more, while attempting to get the best possible recordings. Here's some interesting ones I found with just a quick scan this evening, from the weird to the sublime:
"A Duke Ellington Panorama" by the Duke Ellington Orchestra (1943)
"Minnie the Moocher" by the Cab Calloway Orchestra (1931)
Teddy Wilson and Billie Holiday (1937)
"Doctor Jazz by Doc Evans (1959)
"Sugar Foot Stomp" by Connie's Inn Orchestra
"Tokyo Boogie Woogie" by the Columbia Tokyo Orchestra (1953)
"I Want a Pet Hippopotamus for Christmas" by Vicki Dale with the Peter Pan Orchestra (1953)
"Chop Suey Mambo" by Alfredito and his Orchestra (1954)
You can view, search and download from the entire collection here. There are literally tens of thousands of them, so carve out some time to explore. And feel free to post here any awesome finds.