As weird as it is, I think it was the attitude of my former "fellow" Christians that started me on the road to doubt. Even though I've got a bachelors in Physics and have generally held a belief in evolution and big bang cosmology for most of the believing stage of my life, it really wasn't science that brought up questions(cognitive dissonance at its best). I think I've always generally never had a connection with anyone in any church I had ever attended. Mainly since most Christians, especially in the south, are non-intellectuals. But I think it really started when I began listening to extreme metal. I couldn't understand how anyone could look down on something that I loved so much and felt so natural to listen to. I can't tell you how many people have told me that its "the devils music"(even though most of the lyrics are socio-political).
Of course later on I did my research and discovered how ridiculous my former beliefs were. So who or what started you on your path to disbelief?