My favorite artist at Christmas is Karen Carpenter....love her voice..
The Carpenters' "Christmas Portrait" album, on A&M Records. I literally never fail to get goosebumps when, after the 3 minutes or so of the choral and instrumental music that begin the album, her voice breaks in with the sustained first note of "Christmas Waltz." It's absolutely gorgeous.
There's a double CD entitled "Christmas Collection," but "Christmas Portrait" distills it down to the best of the best.