We don't need to insult any opera singer's crossover Christmas album here. Everyone's gotta eat. But when it comes to service-y classical music, don't forget that few can beat Bach on substance (or quantity). The number of sacred cantatas alone could keep you busy for days; the best cycles are quite pricey to acquire on disc, but easy to hear on Rhapsody. The Sinfonia to BWV 29, as conducted by Nikolaus Harnoncourt on his early cycle for Teldec, leads this playlist (and will probably have you clicking around to hear more). Masaaki Suzuki's survey of cantatas for the BIS label is also worthy of investigation.
On the vocal tip, remember that soprano Leontyne Price once put over some great holiday Bach in an album with the Vienna Philharmonic, conducted by Herbert von Karajan (who also has a memorable version of the Nutcracker Suite to his credit). Lorraine Hunt Lieberson made her mark on an aria from BWV 30. Outside Bach, Benjamin Britten's Ceremony of Carols and John Adams' contemporary oratorio El Nino have entered the seasonal literature. And Nico Muhly's brief but potent "Bright Star Carol," as sung by the Choir of Jesus College, Cambridge, carries on the tradition of graceful, thoughtful music that steers well clear of pandering. Enjoy.