This is a great activity and way to recycle your christmas cards!
If you have a large circle punch or square punch (Stampin UP sells these- ehem.. or you can just come over and borrow mine. :0P )
Take your card assortment and punch out one or two windows. Place cards and punch-outs in a zip lock bag.
Great quiet activity for church or doctor appointments! Have your children match punch-outs to appropriate card. I found this activity here.