How have I missed this site?
Classic Television Showbiz has Christmas episodes of dozens of old TV sitcoms and radio shows. There's Dragnet, Milton Berle, Beverly Hillbillies, Addams Family, Howdy Doody, Brady Bunch, Honeymooners, Munsters, Three's Company, and more. Over twenty Christmas episodes of the Jack Benny radio show. (That's Benny playing the Christmas fiddle.)
(I found this on WFMU's Beware of the Blog.)