The Raveonettes - The Christmas Song (2003 digital single)
Giant Drag - Silver Bells (2007 mp3 download)
Yeah Yeah Yeahs - All I Want For Christmas (2008 mp3 download)
The Long Blondes - Christmas Is Cancelled (2006 promotional single)
The Creatures - Red Wrapping Paper (2001 subscription single)
The Knife - Christmas Reindeer (2006 mp3 download)
Goldfrapp - Winter Wonderland (from the 2008 Starbucks compilation Winter Wonderland)
Rilo Kiley - Xmas Cake (from the 2003 compilation Maybe This Christmas Too?)
Camera Obscura - The Blizzard (2009 single)
Lucky Soul - Lonely This Christmas (2007 digital single)
The Pipettes - In The Bleak Midwinter (2004 promotional single)
Nellie McKay - A Christmas Dirge (2007 mp3 download)

LISTEN: http://8tracks.com/sexton...-christmas

Happy Holidays!

So they aren't all strictly indie artists and the total headcount is more than 12, but you get the idea.
[Edited 12/24/09 11:38am]