A rare selection, but I get a kick out of "The Chipmunk Song" by The Lost Dogs.
Also like Emmanuel by Amy Grant. Also also Carol of the Bells (Ring Christmas Bells)
"If you think something is impossible, check your assumptions." -- Atlas Shrugged
I can't believe no one mentioned any songs by the Trans-Siberian orchestra.
"Wizard in Winter" comes to mind of course.
or also the Hanuka songs by Adams Sandler 
I have a KROQ CD at home that has some great bits, like Johnny Cash reminding folks not to kill on Christmas, but accepting that Elmo and Patsy perhaps deserve to die. There's also "Henry Winkler's Holiday Wish" and recurring character Michael the Maintenance Man's "Me and Mrs. Clause"...
I think my favorite subversive thing is Jill Sobule's cover of "Merry Christmas From The Family" or perhaps "Fairytale of New York" by Kristy McCall and the Pogues. My favorite all-time Christmas song is Nat King Cole's version of "The Christmas Song". I dubiously laugh at every remake.
No particular order:
1) cashing in on christmas -bad news
2) Christmas Wrapping -The Waitresses
3) Walkin' round in women's underwear -Bob Rivers' Twisted Christmas
4) God rest ye merry gentleman -Barenaked ladies and Sara Mchlaclan(sp)
5) Do they know its christmas-Bandaid
Proud member of the Cole-a-lition.
Fighting to make every reality, a better reality.