In a lot of ways Thomas Bezucha's The Family Stone is a cookie-cutter movie of this type, with character types and situations that are typical for the genre. It's a very familiar movie, but what makes it work is how everything clicks together - particularly the stellar cast which includes Diane Keaton, Rachel McAdams, Luke Wilson, and Sarah Jessica Parker.
As much a holiday tradition as A Christmas Story, this third entry in the Griswold vacation series (and the only one in which the "vacation" comes to them) is a movie so funny that you won't mind that it plays over and over again every December.
Jodie Foster behind the camera, pre-superstardom Robert Downey, Jr., and Holly Hunter in a razor sharp performance. Unlike most of the other films on the list, this one takes place at Thanksgiving rather than Christmas, but its portrait of family dysfunction is just as funny.
... Speaking of dysfunction, Wes Anderson's story of the fall (and rise?) of the Tenenbaum family is, for my money, his best film to date. Packed wall to wall with great performances, including Gene Hackman in one of the best performances of his career, The Royal Tenenbaums is a modern classic.
Just edging out Tenenbaums is Arnaud Desplechin's A Christmas Tale, in which a French family reunites after its matriarch (the luminous Catherine Deneuve) is diagnosed with leukemia. Though that might sound like the set-up for a tear-jerker, A Christmas Tale is more of a dark comedy and a very successful one at that.