See if you can add to this list I'm making.

Democrats:

Dixie Chicks
Mary Chapin Carpenter
Pam Tillis
Matraca Berg
Rodney Crowell
Emmylou Harris
Nanci Griffith
Faith Hill
Kathy Mattea
Tim McGraw
Maura O'Connell
Willie Nelson
Garth Brooks
Trisha Yearwood
Kris Kristofferson
Marcus Hummon
Carrie Underwood (based on strong rumors and a confirmation from a friend only)
Raul Malo
Allison Moorer
Steve Earle
Rosanne Cash
Todd Snider
Adrienne Young
Alison Krauss? (while researching, I saw she donated to People For The American Way)

Republicans and/or Bush supporters:

Brooks And Dunn
Sara Evans
Toby Keith (DINO)
Darryl Worley
Clay Walker
Alabama
Tanya Tucker
Lorrie Morgan
Rascal Flatts
Lee Ann Womack (supposedly neither party, but a blind supporter)
Reba McEntire
Vince Gill
Charlie Daniels
Miranda Lambert (very disappointed in this one - she's a great young talent)
Ricky Skaggs
Robert Earl Keen
Travis Tritt
Randy Travis
Neil McCoy
Gretchen Wilson (saw at DU that she was at a Repuke fund raiser)
Loretta Lynn
Hank Williams Jr
Mark Chesnutt
Craig Morgan