A pretty amazing collection of old radio programs – I think pretty much from the US only: OTR.Network Library (The Old Time Radio Network): “The OTR.Network Library is a free resource for Old Time Radio (OTR) fans. We have over 12,000 OTR shows available for instant listening, with 100 more added each week.” An excerpt from their Legal Notices page: “… We believe that the copyrights of the Old Time Radio shows we host on this site have expired. …”
One of my favorites has to be this great American comedy classic from Abbot and Costello recorded in 1947. Note, that the link leads to a realmedia audio file, so you’ll need a thus capable player or conversion utility. Start playback at around 22:22 for the sketch in question. Just before that a lengthy advertisement for a certain well known brand of cigarettes. How times have changed!
Disclaimer: Copyright law varies between jurisdictions, and I’m not a lawyer, so mentioning this or other sources of audio materials here is not intended to be legal advice.