I thought a thread of favorite Christmas poems (or stories) might help to add some needed cheer. In starting I offer a work I really love, that for me stands far ahead of the rest:

A CHILD'S CHRISTMAS IN WALES by Dylan Thomas

(too long to paste-in here, so here's the url for a beautiful presentation of the piece):

http://www.bfsmedia.com/MAS/Dylan/Christmas.html

I've always liked The Gift of the Magi that Anna mentioned, and The Little Match Girl. I remember thinking, as a child, how sad it was that she died, but the way it was written made me know that she was ok.
As to a poem, there are too many childhood memories for it not to be "Twas the Night Before Christmas"!

Stern poetic justice shall be meted to those who would deny the existence of Santa Claus:

In Baltimore there lived a boy, / He wasn't anybody's joy.
Although his name was Jabez Dawes, / His character was full of flaws.
In school he never led his classes, / He hid old ladies' reading glasses,
His mouth was open when he chewed, / And elbows to the table glued.
He stole the milk of hungry kittens, / And walked through doors marked No Admittance.

He said he acted thus because / There wasn't any Santa Claus.
...
Yet people pardoned every sin, / And viewed his antics with a grin,
Till they were told by Jabez Dawes, / "There isn't any Santa Claus!"

http://www.huumor.com/article.php?sid=15 tells the full story of Jabez's horrible fate.