It wouldn't be a true list of nerdy holidays if Festivus wasn't on here.
Festivus, as popularized by the hit T.V. show Seinfeld, is a holiday for people who have had too much of the holiday season. Don't worry if you think it will take too much time to celebrate Festivus; Festivus is all about streamlining the holidays.
So instead of buying and decorating a tree, you get an aluminum pole with a high "strength-to-weight" ratio from your local hardware store. Instead of buying presents, you air your grievances with the rest of your family and challenge one another to feats of strength, whether it be reading something without glasses, lifting something heavy, or wrestling one another for superiority.
And, if you celebrate it just right, you may find yourself with a Festivus miracle on your hands. What that is, I couldn't tell you, but you'll know it when you see it.
If you don't want to take it that seriously, you could always get a few friends together, roast one another, and enjoy a nice little holiday of non-commercialization, all while sitting around an aluminum pole.