Hey, every philosophy or intellectual movement has its radical adherents & its schisms. But you can't call atheism a religion simply because there are variations of atheism like there are different religions.
Call them both philosophies, but they're not both religions. "Religion" implies worship, usually of a supernatural person of some kind, which is something an atheist would have a hard time getting excited about. :-)
Jenny, it's a long read, but post 161 presents how I deal with the defining of religion and how I come about mine.
Qwinn