In Hercule Poirot's Christmas Monsieur Poirot plans a quiet Christmas at home in his London flat until the boiler in his building breaks down leaving him with no heat until after the holiday. As his luck would have it, just as he gets this bad news he gets a call from a complete stranger asking him to come to his well-heated country estate. Saying his life is in danger, the wealthy scoundrel prevails on Poirot to join the family for Christmas. I enjoy this every year. It's full of mistaken identities and family in-fighting and murder.
12/12/2008: We watched this tonight, and I notice it is at youtube in parts with part 1 here: (no longer available as I check on 12/1/2009)
The Adventure of the Blue Carbuncle is the only real Christmas story in the Sherlock Holmes canon. The blue carbuncle is stolen from the Hotel Cosmopolitan and an innocent plumber framed for the job. Sherlock Holmes to the rescue! There are Christmas geese, window-shopping for presents for adorable children, an old rich woman who could out-Scrooge Scrooge, and a happily-ever-after ending. We watch this one every year, too.