I've been thinking about this lately. What books aren't holiday books, however, they do deal with holidays in a new way. I can't recall many, but some do mention the holidays in passing. However, the one that really shows it is the Harry Potter series and they do a wonderful job using those holidays to really build the world. Different types of gifts, different types of food, heck they even have different types of beliefs around it.
It got me thinking in my one of my previous books, I had Christmas later in the story, it was a sad scene because of the recent loss of family members and such, but when I wrote it I found something out about my characters. They used the somber attitude and turned it into a great thing, lots of laughs, memories of the deceased and best of all it showed a way for the characters to solve their dilemma in the story.
So have you ever used the holidays in your stories to build the plot and characters? How did it work out for you and what were some of the interesting situations it put them in?