There are lots of themed Christmas snacks that you can get around the parks and resorts- cookies, rice krispy treats (as past posters have mentioned), hot chocolate, and my favorite... cupcakes.
The resorts also sell some of their Christmas "decorations," such as the gingerbread shingles that are identical to those on the roof at the GF, cookies decorated with pictures of children all around the world at the Contemporary, and so on. I remember the Beach Club doing something new last year- they had a little shop in the lobby selling Christmas treats/baked goods. They're great to bring home as well. I know that the deluxe resorts offered lemonade/iced tea and sugar cookies in the lobby last year on Christmas Eve and Day for resort guests. I don't know if the moderate and value resorts do this as well. It was a really nice, thoughtful touch.
Some restaurants choose to partake in more traditional Christmas fare in terms of entrees and desserts. I think Allears does a great job listing all of these places that choose to partake.
The Christmas treats tend to come out around the same time as the Christmas decorations- a few weeks before Christmas. They don't stay around for too long though. We usually stay long enough for New Year's Eve and Day and find that the resorts at least are pretty quick to take down the decorations (specifically the huge tree(s)) in the lobby ~ 1/3.
Have fun!
