The Elf on the Shelf. I never heard of this tradition until this year. I think it started the same year the Patriot Act was signed.
Basically you get a little elf guy who and put him somewhere in your house and tell the kids that if they're bad the elf will tell Santa and he'll send the gifts to China or something. The idea is to move it around so the kids never know where it could be. To be honest it kind of creeps me out. I half expect it to show up taped to the bottom of the toilet lid or suddenly see it in my rear view.