I'm not particularly religious, but i'm far more open/indifferent to the concept as a great deal of vitriolic internet atheists would like; having formerly been one myself before growing up a bit more and mellowing out to a degree as a result.
I celebrate Christmas; mainly with respect to the elements of family, food and gifts. I do find the religious aspect to be interesting though, and would be just as lost without the classic Christmas Carols as I would be without the likes of Bing Crosby's Walking in a Winter Wonderland. I'll even go as far as to say that the traditional Midnight Service is a very enjoyable way to make the transition from Christmas Eve to Christmas Day; despite only making the effort once in every few years.