Perhaps you guys already know about this, but I only just discovered it.
For a long time, I've been trying to get all the songs on the AM 3000, as well as the bubblers. But some of the really early songs have proved extremely difficult to locate (the Fisk Jubilee Singers' 1909 version of "Swing Low Sweet Chariot" is especially difficult). So there have been some holes in my Top 3000 list.
Earlier tonight, I discovered by pure accident the Internet Archive (http://www.archive.org). It's a non-profit digital library that stores all kinds of materials: movies, books, and even music. Well, a couple quick searches provided me with some of those missing songs, including the aforementioned "Swing Low." If there's anyone else out there looking for stuff like this (AND IT'S FREE!), I highly recommend it.