I'm really more agnostic than atheist -- I lack the core certainty of a lack of divinity, though I find an atheistic universe far more plausible than a theistic one -- but Christmas has always been a big deal to me. I've been culturally brainwashed to relate the supposed anniversary of the birth of a baby in the desert (which, assuming there's an historical component to the story, most likely would have happened in late March as the only reason to spend the evening out in the fields with the sheep is if they're giving birth which happens in the spring) with pine trees and snow, but who said holidays need to be logical.
I essentially grew up in a Norman Rockwell painting, and Christmas turns me into a non-materialistic 4-year-old. Decorating the tree, setting up the lights, helping set up my mother's Christmas village, baking cookies and the like all set the stage. Christmas Eve itself always revolved around carols, the last of the baking, wrapping presents, a candlelight church service primarily featuring religious carols, and a walk home looking at the lights, often accompanied by snowfall -- there are certain advantages to having grown up in the suburbs of Buffalo. It's a little different these days; my mother died some years back, and now my father lives in Florida in the winter so I spend Christmas where it's in the 60s and the natives still wear scarves and mittens despite that, but some of the emotional attachment still exists. And some of the traditions, like our standard Christmas morning breakfast (fried potatoes, scrambled eggs, and polish sausage all cooked in the same skillet), still hold.
Christmas is one of the few times a year when the majority of people try to reach beyond their normal limitations and be a better person. Charitable giving spikes, and not simply because others are watching, but because many take the time to reflect on how good they really have it compared to what could be, and decide to help out the less fortunate be it with time, money, or possessions they no longer use very much but others might. It's also the only time I can count on my brother, father, and me all being in the same house; it happens some summers, but less reliably. Many Christians complain about the secularization of Christmas, but I think it's important to make a distinction between the secularization and commercialization, and it's really the latter that most of them mean.
For those of your worried about the lack of religion in the holiday as celebrated by many, I suggest you turn your worry to Easter instead. From a religious Christian perspective, Easter is the much bigger holiday. As my dad likes to say "Everyone's born. Remarkably few come back from the dead."