This oped in the New York times traces the origins of a couple of the Christmas traditions.
First, the tradition of giving gifts at Christmas:
... the Dutch Christians of [New York City] ... kept alive an old memory — that a kindly old cleric brought little gifts to the poor in the weeks leading up to the Feast of the Nativity ...
The elves who help Santa Claus:
The new Santa also acquired a host of Nordic elves to replace the small dark-skinned boy called Black Peter, who in Christian tradition so loved St. Nicholas that he traveled with him everywhere ... the real St. Nicholas first came into contact with Peter when he raided the slave market in his hometown and railed against the trade. The story tells us that when the slavers refused to take him seriously, he used the church's funds to redeem Peter and gave the boy a job in the church.
And the tradition of hanging stockings at the fireplace:
There is quite a bit that has been lost in the translation from the Dutch St. Nicholas to the American Santa Claus, don't you think?
And what of the ... stockings and little shoes that had been hung up to dry by the fireplace? ... Nicholas had heard that a father in the town planned to sell his three daughters because his debts had been called in by pitiless creditors. As he did for Black Peter, Nicholas raided his church funds to secure the redemption of the girls. He dropped the gold down the chimney to save face for the impoverished father.