I don't have materials to post, but I've run the following one shots over the last few Decembers:
1.) Inspired by the Big Bang Theory, the PCs rescued Santa and his elves. It was a pretty straight forward session.
2.) The PCs awoke with no memory. A glowing light pleaded with them - a random assortment of PCs (including a dragon and an intelligent owlbear) - to climb the steepes, battle the beasts and recover some magic dust from a simpleton giant. In truth, they were a bunch of toys that Santa animated and tasked with recovering some of his magic dust from a child. They faced the family cat, climbed stairs, opened a giant door, and eventually beat up a toddler. They dd not realize what they were until after they beat up the toddler and recovered the dust.
3.) The PCs are in a tavern when a Winter Wonderland version of a Jumanji game begins. The PCs can't leave the tavern and failing to take a turn causes damage... so they are forced to try to win before the game destroys them. The game is mostly mean, but there are presents, a heroes' feast, etc...