Family, friends, music, food, drink, lights and an atmosphere of love/sharing/caring/generosity.
Mad, you mentioned you have no reason to celebrate xmas. We had the same feeling for a while and so hadn't really planned on celebrating it or any other holidays. Then after our DF we rehashed our reasons and... well, now we see no reason NOT to celebrate xmas, even though we're not actually Christian. Here's the link to our rationalization.