National Jukebox
There is big news today for those interested in music and the voice - both classical and popular - with the unveiling of The Library of Congress' new online collection of recordings. With the back-to-the-future title of National Jukebox, it makes an incredible amount of recordings available.
My own quick search using the word 'Caruso' brought up 178 recordings of the great tenor which can be listened with the touch of a key. Ready to dive into its digitized depths? You can do so here. I can only imagine that this resource is going to expand further, which should excite the living daylights out of every music lover as well as give hope to those who bemoan the death of the classical arts. Heck. At the very least, if you can get to a computer in a public library you can hear great singing for free.