This is my favorite Christmas song. I was reluctant to post this version because it's produced by Phil Spector, who has done some awful things (and not just what he went to jail for). I could post Buble's, or U2's, or even Mariah's, but... No. It has to be Darlene Love.
Please don't think of Spector when you hear it. Think of Ellie Greenwich and Jeff Barry who wrote it; The Ronettes, The Blossoms, and Cher who sang backup on it; and Hal Blaine, Leon Russell, Sonny Bono, Niño Tempo and the many others who played on it.
P.S. The best part is at 2:06.