As for Atheism not being a religion: I'm going to argue that is.
I have heard that "Not collecting cards isn't a hobby", but not collecting stamps is simply stating the hobby you /don't/ have. Atheism is to religion what 'sitting around doing nothing' is to hobbies, or what 0 is to numbers.
Also, it's not like Atheists don't believe anything. To be an Atheist you have to consciously believe that deities don't exist.