I'm from the UK and basically a product of a secular upbringing, my parents are agnostic and non-practising Mormon, so religion was never really brought up around me. I effectively never had faith/belief in a God, I've never felt the need (or wanted) to believe in a celestial deity/deities. Although it's only in the last few years that I've properly thought about my lack of belief in a deity, and examined the evidence/arguments for/against a deity's existence and found all the ones for a deity's existence rather... illogical, very flaky and unsubstantiated.
My lack of belief has influenced my life quite a bit, following discussion boards like these piqued my interest in biology and gave me a lot of extra information outside school curriculum that I found really interesting, and it's why I'll be studying Zoology + Animal Behaviour at university pretty soon.
In general life my lack of belief has never really been an issue, in the UK most people are either non-practising religious or simply don't concern themselves with religion. I have a few religious (and 1 or 2 fundamental) friends, but again religion is rarely an issue, and even when it is the discussions usually get quite interesting and no hard feelings afterward.