Today is the First Sunday of Advent, the beginning of a new liturgical year in the Western Church. Here's a quick explanation of the season from the old Catholic Encyclopedia:
AdventEWTN has what looks to be a very nice little page with succinct explanations of different Advent traditions, plus an Advent calendar with short Bible readings, reflections, and suggested prayers and acts of love for each day.
(Latin ad-venio, to come to)
According to present  usage, Advent is a period beginning with the Sunday nearest to the feast of St. Andrew the Apostle (30 November) and embracing four Sundays. The first Sunday may be as early as 27 November, and then Advent has twenty-eight days, or as late as 3 December, giving the season only twenty-one days.
With Advent the ecclesiastical year begins in the Western churches. During this time the faithful are admonished
* to prepare themselves worthily to celebrate the anniversary of the Lord's coming into the world as the incarnate God of love,
* thus to make their souls fitting abodes for the Redeemer coming in Holy Communion and through grace, and
* thereby to make themselves ready for His final coming as judge, at death and at the end of the world.
I went out and bought an Advent wreath yesterday. It's not exactly traditional, but it is quite beautiful. It depicts a Nativity scene, with an angel, a shepherd, the Magi, and Mary and Joseph all adoring the baby Jesus. I've always loved Nativity scenes, so it was a natural choice for me. Jeanette and I blessed it and lit the first candle last night.
I think it will be good to try to celebrate Advent as a season unto itself, a season of eager longing and spiritual preparation for the coming of Christ. It's not the Christmas season yet (that comes after Christmas). The wonderful Father Bernhard Blankenhorn gave a good homily to this effect a couple years ago at Blessed Sacrament Parish in Seattle, and Father Robert Barron has posted a typically good video on the spirituality of Advent: