As I was growing up I attended several congregations of the Church of Christ in Alabama. The churches I attended never had a paid preacher (preaching was done in rotation by several male members of the congregation for free) nor any sort of hierarchal authority but nonetheless the congregations across Alabama (and to some extent, across the country and even the world) maintained connections with one another such that members of the church of Christ in Birmingham often knew members of the church in small towns a couple hours away.
The absolute, number one focus of these churches was to keep themselves and their church service in complete accordance with what the Bible taught. We had no Sunday school, no musical instruments during the church service (singing was a capella) and the members of the church cited verses from the bible (or, sometimes, a total absence of verses that condoned such things) to support these prohibitions. Over at Less Wrong you can find a community of people who are dedicated to, at all costs, eliminating their own bias and following logic and evidence. The church of Christ is very similar with the exception that they are dedicated to following the bible (which they consider to be well-evidenced, and proofs of prophecies and such were regularly presented).
Let me offer a few recollections to show you what it was like:
I knew an elder who was subjected to punishment during World War II. He was asked how he would contribute to aiding his country during the war and he responded that he would go to the battlefield and collect the wounded for further treatment. But there was a catch: he said he would pick up the bodies of the Germans as well. He reasoned that the German soldiers were people too and as a result he could not, in good conscience, allow them to die (thou shalt not kill). As a result he was ordered to do hard labor for several months (apparently the US had some sort of work camp set up for people like him).
After learning about the pagan roots of Christmas, my parents quit celebrating it and my Dad even preached a sermon on why it was wrong, which did not go over well with a few of the members.
As a child I was frequently taken to the library, allowed to read whatever I wanted (my mother had read the Qu'ran and felt it was good for me to read a broad variety, too). My mother also told me not to simply trust everything I was taught, but to keep an eye out for things that might be wrong with our own religious practices, just in case we weren't doing things exactly the right way.
So, the peculiar version of Christianity that I was raised in laid the groundwork for me to become a freethinking atheist. It took only a baby step to go from my former belief that all other churches in the world were a distortion of the truth to my present belief that all religions are fundamentally wrong.
I only made a baby step when I, as someone who believed in basing my beliefs directly on evidence (of which I had assumed the scriptures were a subset) started to turn a skeptical eye on the Bible.