OK I'm heavily into the classical genre when it comes to Christmas music, so how about Benjamin Britten's "Ceremony of Carols"; anything at all done by the group Anonymous 4; "A Renaissance Christmas" recorded by Boston Camerata; and anything by John Rutter and the Cambridge Singers.
On the more contemporary side, I like George Winston's "December"; A Winter's Solstice V; "The Carols of Christmas" a Windham Hill Collection, 1996, and "Celtic Christmas Spirit" done by Caroline Peyton produced by Spring Hill Music Group, 1998.
My taste in Christmas music is about as eclectic as my taste in music in general. It goes from the sublime, Anonymous 4 doing 15th century Hungarian Christmas songs, to the ridiculous, Trisha Yearwood doing a very torchy "Santa Claus is Back in Town".