a few of my favorites:

Boney M's medley of "Mary's Boy Child"/"O My Lord"

Allison Krauss's fiddle version of "What Child Is This?"

"Mary, Did You Know" sung by Kathy Mattea or by Clay Aiken

any up-tempo rendition of "Joy to The World"

Barenaked Ladies and Sarah MacLachlan's medley of "God Rest Ye Merry, Gentlemen"/"We Three Kings"

Dan Fogelber's original composition "The First Christmas Morning"

The Muppets and John Denver singing "Christmas Is Coming"