Most people assume Christmas is a faith-based holiday and, as such, can't be celebrated in a nonreligious way. You have to believe in Allah to celebrate Ramadan, right?

Although Christmas has largely been observed as a Christian religious holiday, that has changed dramatically over the years. The holiday already included many elements borrowed from other religions, which made it easy to celebrate Christmas without reference to religion.

Family Gatherings at Christmas

Large numbers of people have family gatherings during the Christmas holidays. Since so many people have time off during these holidays, it's a good excuse to visit and spend time with family. Although many go to church as a family, there are plenty of things people can do as families that are completely secular: dinners, gift exchanges, ice skating, volunteering at a soup kitchen, holiday shows, etc. You could make the Christmas holidays an annual family reunion to strengthen familial ties.

Christmas Parties

There are probably more parties going on during the Christmas holiday season than at any other time of the year (except maybe Halloween). There is also nothing intrinsically religious about Christmas parties; in fact, many parties which occur in offices and schools are entirely secular because of the religious diversity of those who attend. If you're looking for an excuse to have a party, this is as as good as any.

Food

The Christmas season has developed an entire line of foods — mostly sweets — that only appear during this time of year. Little, if any of it, is religious in nature, so celebrating this time of year with special foods and meals is an inherently secular activity. Food might not seem like much of a celebration, but getting together with others to make and enjoy food can be very important socially, emotionally and psychologically.

Decorations

People spend a lot of money to decorate their homes for Christmas. Although there are lots of religious decorations out there, you can also find plenty of secular decorations. So if you like decorating the house generally or just occasionally for the sake of change, you have lots of non-religious choices: Santa, reindeer, evergreens, lights, mistletoe, etc. Secular decoration options are abundant precisely because there are significant non-religious aspects to Christmas.

Gift-Giving

The most popular Christmas activity is exchanging gifts, and it doesn't have to be abandoned to have a secular Christmas. There's nothing about Christmas presents which is inherently religious or Christian. The only way for the gifts to have any religious meaning is if you personally invest them with one; otherwise, the gifts are simply of the sort which you might give other times during the year.

Christmas Shopping

The least religious aspect of Christmas is probably the one which involves the most time, effort, and money: shopping. There's nothing the least bit Christian about Christmas shopping, so if you're someone who actually enjoys the sights, sounds and smells of shopping at Christmastime, you can do so without wondering if you're just giving in to popular religious celebration. Indeed, by participating in the commercialization of Christmas, you're helping to diminish its religious aspects.

Charitable Donations & Volunteering

Except for attending church services, donating money or time to charities is the one activity which could be the least secular because so many charities are religious. This doesn't mean that charity is exclusively religious, though. You can celebrate Christmas in a charitable manner without giving anything to religious charities - there are secular charities out there if you look. You can donate your time or money to a charity of your choice without feeding any religion.

New Year's Celebrations

The Christmas holiday season isn't just Christmas, but also New Year's. People have lots of parties and family gatherings around this date as well, and it's even more secular than Christmas. There's nothing at all religious or Christian about it, so there are lots of ways atheists and non-Christians can celebrate it without any references to traditional Christian activities.

Why You Don't Have to Be Religious to Celebrate Christmas

Christmas is a cultural rather than a religious holiday. This does not mean that there are no religious elements to Christmas — on the contrary, there are many religious aspects to Christmas. This is what we should expect from a cultural holiday because religion is an important aspect of culture. Culture, though, is more than just religion, and this means that there is more to Christmas than just religion, even though it's a day ostensibly set aside to celebrate the birth of Jesus Christ, the Christian savior. In fact, significant portions of Christmas celebrations today don't originate in Christianity at all.

No one celebrates every possible aspect of Christmas: some hang mistletoe, some don't; some drink eggnog, some don't; some have a creche, some don't. Everyone has traditions which are more meaningful than others, and most create some of their own "traditions." The result is that everyone picks and chooses certain aspects of Christmas to celebrate and others to ignore. If you want to celebrate a secular Christmas, just ignore the religious options.

There's plenty to choose from, though the Christian Right would have people believe that there is only one "definitive" set of traditions which represent a "real" Christmas. In effect, they would like to freeze Christmas as an idealized postcard version of the holiday, circa 1955, with "White Christmas" playing on an endless loop in the background.

This would drive most people batty and it's not the sort of Christmas that anyone celebrates. It's doubtful anyone ever really celebrated Christmas in this manner — it looks more like the manufactured nostalgia people create in order to feel better about their past. It's sometimes easier to get people to accept an ideology being imposed on them if they are told that it's "tradition" and the way things used to be rather than the truth: that it's a just a simulacrum of reality based upon an ideological preference for certain power structures.