The topic of religion didn't come up for us until my daughter started school (kindergarten). We were living in the Bible Belt at the time and my sister had just become "born again". I bought my then 5 year old some age appropriate kids books (Amazon is great for this) about various religions (the big 6). That was enough for her; it answered her questions without giving her an opinion. And that's important to me. I want her to have critical thinking skills. To me that means being able to form your own opinions. When she asks me questions that are "hot button topics" I point her in the direction of information, and let her peruse it at will.
Every so often the topic of religion has come up over the years (usually after visiting her aunt/cousins, or when a new kid came into her class that wasn't christian) and we'd talk again about the big religions, and I'd get her some more books if she was interested.
We avoided bringing up that we (her parents) were atheist until she was about 8. One of my sister's told her she was "doomed to hell, you poor thing" and the other tried to convert her behind my back. Nothing pisses me off more than someone threatening my kid. It resulted in a very frank conversation between me and my daughter about why exactly I would never be a christian (basically, it's fucked up shit, and I read to her straight from the Bible) and then why I don't believe in a god, period. As far as "religion" goes I'm a humanist.
Over the years she's gone to several services at different churches, either with babysitters or family. She hasn't asked to go back to any of them. At one point I took her to a Sunday Assembly service, but neither one of us were feeling it so we haven't gone back.
We talk more openly about religion now that she's older (10), specifically christianity because of my sister/her cousins, and she seems pretty uninterested in being apart of the whole thing but I realize that could change.
I don't care if my daughter tells me one day "I believe there is a supreme being." I DO care if she's sucked into some religious group using recruiting tricks, coercion, fear, peer pressure, false promise, etc. I don't like the idea of my daughter being taken advantage of to promote some organizations' agenda/cling to power (sue me).
And that's my two cents.