I do know that not all our ESL students celebrate Christmas, so please only use with those students who you think it may be appropriate. My personal opinion is that if Christmas is going to be celebrated in a school then all religous holidays that the students in the school celebrate should be celebrated too. I once worked at a fantastic Infants school in London where all major religious holidays were celebrated and it was great to not only learn about the different celebrations, but also to celebrate along with my students and get to know more about their culture.
Here are just a few sites - if you know of any other good sites let me know and I will add them to the list.
Boggles World ESL
BBC Kids Learn English - Christmas (and search Christmas on the site for more vocab and games)
Christmas
ESL Kids Stuff - Christmas
Isabel's ESL Christmas
ESL Games Plus