Greta Christina has a terrific article highlighting several reasons atheists should be celebrating this time of year:
Reason #7: Holiday traditions are comforting. The human need for tradition and ritual seems to be deeply ingrained. It’s comforting to do things at the same time every day or every year: things we did as children, things our parents and grandparents did. It gives us a sense of continuity, of being part of a pattern that’s larger than ourselves, of passing along ideas and customs that we hope will live on after we die. For those of us who don’t believe in an afterlife, that last bit can be extra important. And when those customs and rituals are about joy and celebration and people we love and so on, that makes it extra nifty.