I always put my ongoing campaigns on hiatus during the break, as everyone is so busy over Christmas and New Year. So, our last session is the first Tuesday of December, and the next is the third Tuesday of January (effectively 'missing' two sessions).
That said, we do also try to organise a special one-off "Christmas Game". It didn't happen last year, but this year's event took place yesterday. It was a "Serenity RPG" one-shot in which the PCs had to arrange to break one Mal Reynolds out of a prison facility. Much fun was had by all.