A friend of mine posted a few letters her kids at school wrote to Santa. She had a few skeptics this year. Check her blog for more, but here's my favorite:
Dear Fake nonreal Santa,
I don't beleive in you because you're a over weighted large person who goes down chimnys. You would get stuck in chimnys because you suposedly eat cookies that kids who are not me belevie in you. Christmas isn't about you Its about God and Jesus you shouldn't steal children away by giving them presents. You better stay away from my house because Christmas is about God not you. But I also sorta beleve in you because I feel terible being mean to you if you exist. If your real please don't put me on the notty list because I'm realy a nice person.