Some people just love arguing about classifying non-believers; who is a deist, who is an atheist, and who is an agnostic. However, I think that the only real and meaningful question from the viewpoint of any organized religions is: "Are you one of us, or are you not".
If you don't buy into the particular version of a Single Final Truth that is offered by a religion, you are out and useless for that religion. Then you simply will not be preserving and forwarding that particular religious idea.

From the viewpoint of an organized religion, it is really a quite trivial matter if you are you doing this because you are an atheist or a deist or an agnostic or a follower of a different religion. You are just of no use for that religion.
For example, many of the founding Fathers of the United States opposed organized religion. This is true, even if they still believed in the existence of some kind of universal 'being' as some kind of Original Reason for the existence of the universe.

Many of them were deists. Deists have a notion of a universal creator -spirit, but they do not believe that any religious text can offer any kind of Final Truth. In the end, they did build strong barriers between the state and religion. In practice it did not matter that they were deists and not example atheists, as the result was quite the same from the viewpoint of the organized religions.
The real and important divider here was not the division between atheist or agnostic or deist. The big division is between the believer and non-believer for a particular religious creed.

The current widespread religious memes have survived for thousands of years because of their ability to take over completely minds of people and propagate through them to new minds. If this process stops for any reason, the religion is doomed, but the reason why this happens is not really important form the vantage-point of an individual religion.

Thomas Paine - Wikipedia

A extremely crucial moment comes when you start suspecting that there is no single Unshakable Final Truth, but that even many parallel lesser truths are possible. At the moment, this happens all religions have really lost their game on that individual, even if the person could still think, for example, that there might be an original creator that has since that not concerned itself with out universe.
So the real divider is the attitude towards the idea that there can be One Final Truth in existence. For example, communism can be in this respect quite similar carrier of One and Only Truth as Christianity or Islam.

The big thing (for me personally at least) is taking a critical view on all possible Final Truths and accepting the possibility that the world can be seen in more than one way at the same time. World just is best changed painfully slowly, laboriously and issue by issue to the direction of better social equality and better accepting the versatility of life and human endeavor.
I believe that I can well work together will all kinds of agnostics, deists and even those theists who have renounced the demand for others to succumb to a One Final Truth. In practice, such theists are extremely rare. This kind of theism is usually only a half-way house on the way out.

I freely label myself as an atheist. I also freely admit that saying will put me in a locker of its own. But this particular locker does contain people from all possible world-views, social backgrounds, political movements, races, ages and genders. In fact, I do not find it limiting at all.
Atheism is in the end just lack of belief in any supernatural Final Truth. It can also just give people elbow room to believe that there can be many competing good and worthwhile truths. Most of all one can understand there can exist many different visions for a better society at the same time side by side.

If we are not locked into a single truth, we are finally free to choose the ones that seem serve best the interests of ourselves, our family, our social group and most of all our society.
A real freedom from a belief in single Final Truth can free a person to understand that many kinds human ideas can openly compete on intellectual and factual level for influence in a society. A true democracy just is not attainable without such a belief.

In the end atheism in itself does not contain any kind of code of conduct or direct instructions for building and maintaining a society. The important thing is not to allow oneself to be completely locked in ready-made, spoon-fed system of thought like a modern mainstream organized religion too often still is.
Of course, also all atheist will have personal ideologies, but hopefully it will be chosen more on the merits of the ideas themselves and not just by forces of tradition.

I also think that freeing one’s mind from the bronze age belief systems can lead to better use of rational reasoning, lead to a truer analysis of our reality and to the better use of all of the human resources that are present in a society.
A perfect society is a quite unattainable goal anyhow. But the process of just striving for one can make this planet a bit better place, I think.

(This piece was completely revamped in 29th of May, 2012)