We've had ours in the car for a few weeks. We tend to like oldie ones (my dad played them on christmas morning so reminds me of that)
Some are -
Chestnuts roasting on an open fire
White Christmas
It's beginning to look a like christmas
Ther's no place like home for the holidays (my favourite)
Silver bells
Santa Claus is coming to town (with beginning intro - I just got back from a lovely trip, along the milky way....)
Here comes Santa Claus (right down Santa Claus lane...)
Rudolph the red nosed reindeer
I saw mummy kissing Santa Claus
Walking in a winter wondeland (another favourite)
Frosty The Snowman
Oh come all ye faithful
Little Drummer Boy (Bing Crosy & David Bowie)
Hark The Herald Angels Sing (another favourite)
and then all the more usual modern one, which I'm sure others will mention. Those above I think are more rare to find in shop compilations.
hth