Slower ones would be tricky. Silent Night is probably a good one. But generally I have found Christmas tunes to be of the up tempo, cheerful variety more suitable for Viennese Waltz, especially the song "Christmas Waltz," which is a good one, by the way.
Has anyone noticed the trend for Christmas songs to get "jazzed up" in the past few years to allow some swing and Fox Trot to be used? I guess it gives good variety for a Christmas dancing party.