Well, I've celebrated Yule* alone for the last ten years or so, because all my family live at a distance, and can't travel to where I am in midwinter because of threats of snow and ice.   I celebrate by singing to myself, meditating silently on new light coming into my life, and taking part in Mudcat's Secret Santa game. In recent years, I've made up a few Solstice-themed carols, but nothing has come to me this year.

Like Mrrzy, I celebrate the soltice because it happens, whether you believe in a deity or not (or even if you're human or not), and shortening daylight is depressing, and lengthening daylight is cheering, and is as good a reason to celebrate as any. I grew up celebrating Christmas, but I remember Mother telling me, when I was about 8 or 9 that all the common icons of the holiday originated as part of the solar festival. And when I was a teenager, for a few years, she would host a neighborhood-wide potluck party for the afternoon of the shortest day, and tried to lead everyone in a raucous cheer as the sun went down... Some joined her, some looked at her in bewilderment.

And yes, gift-giving and gift-receiving (and learning to do both graciously) is a big part of it. Such mutual exchange doesn't happen at birthdays, or if you just give gifts "whenever."

*(I call it that mostly because I like the sound of the word, and have read on several sources that it comes from the Anglo-Saxon "geol," meaning "coal" and links it to the fire-festival. But I also agree with McGrath that "Christmas" is as perfectly fine a name for December 25 as "Tuesday" -- many use that name without flinching, even though very few actually worship Tyr, any more...