Verified answer

Anything by Transiberian Orchestra or Manheim Steamroller

Examples)

Transiberian Orchestra

1) http://www.youtube.com/watch?v=4vNcGlM8O3I

2) http://www.youtube.com/watch?v=XFLOh44P5z0&feature...

Manheim Steamroller

1) http://www.youtube.com/watch?v=cCsQX-TY-dQ

2) http://www.youtube.com/watch?v=NZ5X4ZAlAnw&feature...

Vince Guaraldi - I love the Charlie Brown Christmas Movie instrumental music.

The soundtrack to The Holiday is also really wonderful. I love Hans Zimmer's music in this movie. You would probably need to watch the movie in order to really appreciate it as Christmas music though.

I don't know anything about instrumental but I have a good Christmas song in mind:

http://www.youtube.com/watch?v=LUjn3RpkcKY&feature...