...And plenty of atheists who go to church. I know several, and occasionally darken the door of one myself.

Why would an atheist do that?

Actually believing in god the way American Christians understand those words has not been a major part for many religious through history. Religious are about a lot more than just a bearded father figure in the sky.

Social activity.

Basically what Dan said. Community.

You still can't admit to atheism in many (most?) areas of the country without pretty severe social penalty.

Hopefully this is changing, but I think it's less that is atheism growing and more that people are becoming comfortable admitting what they really think.

How can you not affiliate with any god and not be an athiest?

Surely (not athiest) => theist => (believes in a god) => (has a religion)

This is going to sound really dumb, but it's how culture works so bear with me.

I'm nonreligious, I don't care to discuss it or think about religion as a part of my life, but it's okay if others want to be religious themselves.

Why don't I want to be labeled atheist? It's looked down upon and many hardcore atheists are exclusionary.

You know how when someone insists on it being GNU/Linux, but most people don't care? That's why I'm nonreligious (but technically atheist).

I used to tell people that I was an atheist, and my wife told me I was more of a "fundamentalist atheist" because I wanted everyone else to be too.

Now I call myself a "Reformed Fundamentalist Atheist" because it captures that I don't care anymore (reformed), and it sounds enough like a real religion that people seem to accept it as one.

In the spirit of many of the good things on the internet, the Reformed Fundamentalist Atheist church (RFA) is of course an open source religion, under the MIT license :)

Lol, sounds legit.

I have known several people who did not subscribe to any particular religion - actively shunned some - but described themselves as "spiritual". Others are self-described agnostics. Being an atheist is usually considered an active choice, not a passive one.

I think it's more like: made a decision about god? if yes and believe there is one then theist else if believe there isn't one then atheist.

A lot of people I think don't care to form a belief one way or another. I'm not sure what that's called.