I picked up a ska Christmas album several years ago on a whim, and it has one of my favorite unusual Christmas songs on it. I'm particularly partial to the lyrics that say, "Some people say where is Santa? Well, you might think I'm crazy, but I've got him in a manger scene bowing down to a baby."
http://www.youtube.com/watch?v=ePNqMouos8c"So Many Santas" from the same album is also good.