Muppet's Christmas Carol is also excellent, as previously mentioned.
A little off topic, but I also associate some non-Christmas films with Christmas, paritculalrly sci-fi:-
It's either Star Trek 4 or Star Trek 6, the intro music sounRAB very Christmassy to me on one of them, and it's always on around Christmas.
Return of the Jedi - still have a VHS tape with "Christmas Care Line - Are you feeling lonely this Christmas? - phone 0161 ... ...." scrolling across Jabba the Hutt's face. So I always associate that one with Christmas.
There are many films they nearly always show at Christmas, so I end up being reminded of Christmas if I see them again - "The Great Escape", "The Italian Job (1969)", "Flight of the Navigator".
I want to see "Christmas on the moon (1959)" some time, it was an episode of an American sci-fi show.
And I did recently see "Feast of Steven (1965)", a light-hearted episode of "Dr Who- The Dalek's Master Plan" which just appened to coincide with Christmas at the time of it's original airing.