Atheism is not a religion. It does not spell out a way of life. It, in and of itself, offers no theory of morality, no hope, and no philosophy of life or meaning. Atheism at minimum means not having a belief in God.
Yet, many atheists, such as myself, can see the advantage of having a system of morality, a source of hope, a philosophy of life, and a way to give meaning. In addition, many atheists see the benefit churches provide in the sense of community. Communities are important for celebrating births and marriages, for commemoration during deaths, for support during hospital visits, for exchanging ideas in developing one's philosophy of life, for examples and mentors for your children, for a broader perspective and lessons in cooperation, and for opportunities for growth and to give service. I also enjoy feeling elevation with others, that transcendent emotion (warmth in the chest, love in the heart, peace in the mind).
So, to meet these needs for those who don't believe in god, atheists have created something akin to atheist churches, although they would not call them that. There are many "churches" in which atheists may feel at home, both real brick and mortar churches and internet communities. Here are a few:
I personally, attend a Unitarian Universalist Fellowship. Not all UU's are atheists, but a good number of them are and many atheists feel very comfortable there.