I often hear some theists say atheism is a religion because the courts said so, even when it doesn't fit the definition of a religion:
Religion: A set of beliefs concerning the cause, nature, and purpose of life and the universe, especially when considered as the creation of a supernatural...
50 Reasons People Give for Believing in a God
http://wiki.ironchariots.org/index.php?title=50_Reasons_People_Give_for_Believing_in_a_God
I'm an atheist, by the way.