Mac OS X only: Freeware program X-MasTree puts a customizable Christmas tree on your desktop, complete with a days-to-Christmas countdown.
If you’re a sucker for decorating every corner of your life with holiday cheer, this is the app for you. You can completely customize the style and behavior of the tree through the preferences, and with a nice winter-y wallpaper, you’ll have created the perfect Christmas desktop. With the days ’til Xmas badge activated, it’s like an Advent calendar for your desktop – without the toys/chocolate.
Originally from Lifehacker