The kids loved doing this on New Year's Eve; they hang on our fridge and we'll do a new one at the end of 2013, etc. Such a great keepsake!
Grab all your Christmas/holiday/winter themed books and wrap them up. Start your countdown according to the number of books you have. If you have 12 books do the 12 days of Christmas and start on the 12th, if you have 20 books you'll start on the 4th..). Each night one of the kids will get to pick a book and open it and then read it together as a family.