Not really Jez. Atheism simply means "without god". It's not that an atheist believes there is no god, more a lack of belief that one exists. I am an atheist for example, and I don't "believe there to be no god"... it's just that for me, there is no god. Catch my drift? It's quite a difficult concept to communicate.
My dictionary has:
religion |riˈlijən| noun -the belief in and worship of a superhuman controlling power, esp. a personal God or gods.
From a purely definitive point of view I would say that atheism cannot be a religion.
