The Slacker in me loves to decorate with snowflakes. Sure they're pretty and festive, but they are also easy to store and you don't have to take them down until some time in March or April.
A number of years ago I stumbled across Dave's Snowflakes, bought the disk and have been cutting snowflakes ever since.
They cover our tree, hang from a huge mobile in our two story foyer (which the girls think is funny because it's a snowmobile) and are sprinkled throughout the rest of the house. When we're done with them, the whole stack stores easily in a manila envelope.
Another benefit is that the project is easily transported. I have a ziploc with a stack of pre-printed patterns and some scissors handy and can take it with when I know I'm going to be sitting in the dentist's office or riding in the car. Just fold and snip away, dropping your scraps into the bag.
Every year I try to add a couple dozen new flakes to the mix. It's fun to curl up in front of the fireplace and make snowflakes with the girls will we listen to books on tape or watch favorite holiday movies. And the best part? If you make a mistake, it's only paper.