Carol by the American Boychoir is a beautiful collection of 13 traditional songs, including "Away in a Manger" and "O Come, All Ye Faithful". The voices are lovely.
An American Christmas is a collection (25 tracks) of carols, hymns and spirituals from 1770-1870 sung by the Boston Camerata, directed by Joel Cohen. This is one of my favorite Christmas CDs. It's different from most that we have. I like the liveliness.
Home for the Holidays by the Eaken Piano Trio, is 18 tracks of mostly traditional music (The Christmas Song, Silver Bells, Ave Maria, etc.) but there were a few I was unfamiliar with. This is perfect for ambient music during the holidays. It is nice to listen to for its own sake but doesn't distract, and I'm not tempted to sing along as I am with so many CDs so I can hold a conversation while this is playing.
Comfort and Joy: Christmas Tapestry Collection with the Regency Singers and Orchestra has 10 tracks of mixed sacred and secular music. Most are vocal/choral, but there's at least one that's instrumental. This is one of my least favorite of our Christmas CDs. I don't like the arrangements at all, and I like the voices on other CDs much better.
Christmas Carols with the Londonderry Singers, for example, is much more to my liking. It's strictly traditional arrangements of the traditional hymns make it easy for me to sing along with -I can even pick out the alto part.