Thanks to Christian History magainze:
Christian History magazine ran a series of articles on the history of Christmas. These are quite readable, yet reliable historically.
"O, Christmas Tree"
History of Christmas tree traditions.
Background on various Christmas traditions, especially nativity scenes and Christmas pageants.
When does Christmas really begin? On the history of Advent.
"Peace on Earth?"
Christmas carols and the Civil War in America.
"Happy (?) Advent"
A basic discussion of Advent, the period of preparation for the celebration of Christmas.
"Why December 25?"
A readable discussion of the origin of the date of Christmas.
"Let Me Count the Days"
On the supposedly Christian origin and meaning of the carol, "The Twelve Days of Christmas."
History of the use of holiday plants, including holly and poinsettieas.
History of the candy cane and its Christians origins.
"The Real Saint Nicholas"
Short history of "Santa Claus."
From the Catholic Encyclopedia online:
An article from the Catholic Encyclopedia . Filled with lots of facts about early Christian celebration of Christmas. Lots on the origin of Christmas and the problem of the date of Christmas.
Helpful Books to Buy:
Among many books on the history of Christmas and Christmas traditions, two by Ace Collins are very readable and fun, yet reflect careful study. These books are:
Stories Behind Great Traditions of Christmas.
Stories Behind the Best-Loved Songs of Christmas.
Ancient "Gospels" and the Birth of Jesus
If you want to read a "whopper" of a ancient "gospel" in which Jesus is a bratty little miracle worker, see "The Infancy Gospel of Thomas."
Another early Christian writing that fills in many of the gaps in the story of Jesus' birth, with lots of legendary material, is "The Protoevangelium of James." This includes the legend of Jesus born in a cave.