If you really think about it there are fanatics on both sides. Religion is really only
a group of people believing in a certain way. Atheism to me is the same way
my beliefs and the right to them. I like to live my life with my own beliefs
so I do not begrudge anyone else in their beliefs.
Well I think that Atheism is not a religion because of the theist trappings that go with not only most of the printed definitions but the common interpretation that religion is based around a god or gods.
But I think there's a more important question that relates to all of this - Should Atheism be a Religion? And that question is a political one. To act as a counterforce to theistic religion should we be working on loosening the common definition. Religion at its heart relies on indoctrination and peer pressure to convince people that they cannot know relevant truth but through the anointed priesthood and offers as a reward for accepting that system of beliefs the protection of its community.
We, as atheists, don't offer that same system. While what we have may offer a far better way to approach life, we really aren't organized to compete with religion. Almost by definition we allow for the community of ideas on specific points to vary widely because, I think, by and large, we all accept that there is no perfect knowledge to be attained in the real world - all we really have is our best estimate at the time we have to use that knowledge. And amongst us all are a very wide array of experiences that might cause us all to have variable knowledge of reality. In that sense we really don't have a common base of knowledge so much as a commitment to reason as the path to enlightenment rather than sending cash to the priesthood.
But should we be working on a codification of principles about which to establish something like a church?
I think what will draw people away from theism is to provide the trappings of religion that most people actually want - the sense of belonging to some form of organization that provides help in a crisis, provides the sense of social identity and worth to people by having a tribe they want to be a part of.
Please forgive my ignorance about the details of this but I believe there was a recent court case where someone was trying to get atheism either classified as a religion - or told by a judge that in order to present the case of atheism as an alternative to the common forms of religion it would have to try to look like a religion to receive equal value in the eyes of the law.
I am also sufficiently ignorant of the gamut of organized atheism's activities to not know if we are actually considering doing what all the organized religions have done - to hold some form of ecumenical council to adopt a codification of the central philosophy as part of establishing atheism as an alternative belief system.
I believe there are common truths regarding moral behavior that we should present as an alternative. I see nominative Christians tolerating insane moral conduct by Islam, largely, I think, because to question Islam's religious laws and moral code would open their own system to review. There are a lot of principles of religion relating to allowable marriages and relationships that can and should be challenged - but not so much in the courts as in the hearts and minds.
And, again, because of my general ignorance of the totality of organized atheism, I don't know if anyone is working on that kind of idea already. We need to be able to provide a reason-based alternative to the authoritarian "Thou Shalt or Shalt Not" nonsense that goes into what we can collectively agree is rational human behavior and couched in a setting of NOT being divine but as the best consensus of our minds today - subject to evolution over time.
There are so many things about our social interaction that I think are largely immutable, protecting children from physical and intellectual harm, not breaking someone else's bones or picking their pocket to borrow from Thomas Jefferson, and many other thngs that I think we can come to agreement on - not as laws but as guiding principles for the "alternative religion of Atheism."
So whether we agree that atheism IS a religion or not - is the right question "Should it Be?"
As far as organizations along the lines you have mentioned, you should look into American Atheists- http://www.atheists.org/ - and the American Humanist Association- http://www.americanhumanist.org/ .
As far as being a so-called "religion," I think the terms "atheism" and "religion" are, and should be, mutually exclusive.