I was by separate parents: my father came from a loose Communist background in Russia and Hungary, having himself been raised by a very traditional Stalinist mother and former Central Intelligence director for a dad. He's ended up being quite anti-religious, but is still technically agnostic. He's also very personally aggrieved with religion for various reasons.
My mother was raised as a Clifornia girl from a rich family over in Los Angeles, though they were more lawyers than they were religious. She just ended up being very loosely Christian, taking me to Church for holidays and occasionally Sunday School. I was passively bored with all that. My dad would take me to a Russian Orthodox church for Christmas sometimes, although that was more for the ritual than the actual religion behind it.
My mother ended up sending me, after years of home-schooling, to a Christian Private school in my area. While I ended up enjoying it and being comfortable with most of the people there, their overt religiosity was essentially what pushed me over the edge. The entire dogma, and the prejudices that seeped into the teachings did not make sense to me. As I read the Bible more and more, I was surprised at how, well...at the risk of offending anybody, how archaic i was, and how much it didn't properly apply to civilization 3,000 years later.
My mother was a little shocked when I accidently slipped one day that I wasn't religious at all, but she got over it pretty quickly. My father, on the other hand, was very approving.
I ended up staying at the school, where only one friend knows I'm not Christian. They're not bad people, once you realize that the religion is not all that's going for them.
...Damn, this longer than I expected.