Stephen Colbert sang the excellent Another Christmas Song, which is part of a collection of parody holiday songs called A Colbert Christmas.  The former was included in iTunes' recent free holiday sampler, which is unfortunately no longer available.  Samples of Colbert's songs can be heard at this iTunes link.  Here's a sample of some lyrics: 
Santa Claus singing on naughty snow
Reindeer ringing in the mistletoe
The manger's on fire, the holly's a-glow
Hear the baby Jesus crying ho ho ho

Hey! It's another Christmas song
Yay! Another oft' returning, royalty earning Christmas song
I've got plenty more so go buy a modem
Log on to iTunes and pay to download 'em
Pay! For another Christmas song
That's some pure gold. #entertainment