Among religious Christmas songs, I love Mark Lowry's (sp?) "Mary, Did You Know?" It could be considered "folk" in the same sense that Bill Staines's or Gordon Bok's songs are "folk." Anyway, it has a real folky sound to it.

(My sister and I both change one line in it, though. The line about "...your baby boy will someday rule all nations" I sing as "... your baby boy can bring peace to all nations?" I originally thought that was the way it was written, and I decided not to change it after I found out the actual line. Sorry, Mark.)