I am not religious, and it's a religious holiday ;-)
Christmas is whatever you want to make of it. Not a Christian? Then it can be a holiday about being thankful for friends and family, renewing those relationships and staying in touch with them.
On a grander scheme it unites strangers and generally is a good reason to remember to stop and thank people, or do that right thing and generally not treat everybody as just another someone else you must interact with to get to the end of the day. I spend it being thankful for what I've been given, what I have, and what I am able to give in turn.