God and Religion are two separate things.
Many people think that without religion, there is no God. I don't know how many times I have been asked "Are you religious?" and when I reply no, they say "So you're atheist?". To which my answer is also "No".
The traditional upbringing that American children receive frequently involves attending a particular church on a regular basis. From a very young age they are taught to think that church, religion, and God are all the same thing. This could not be farther from the truth.
I personally don't understand why a specific religion would feel responsible for specifying every little thing. Couldn't a religion, instead of claiming to know God's qualities, say that they do not know what God is, or what he/she/it is like, however they do know that they believe it's best to behave a certain way. Instead you get a religion that says God is omnipotent, but the future is a toss up (a conflict in itself) and he is divided into three things, the father, son, and holy ghost, and anything else, that varies from this definition, even a little, is WRONG. In that case I guess Homer Simpson hit the nail on the head when he said "What if we choose the wrong religion? Each week we just make God madder and madder". There is no way to know God's qualities and there is no justification to inherently assume that God is human-like. Why does God have to be omnipotent, it creates many problems and it doesn't make sense. Having a belief in God without religion is accepting that there is or may be a God, however you don't feel that a religion is necessary to specify what God is like, or how we should act. People seem to forget that religion (not God) was developed by humans, who are inherently flawed. Religions change, religions get things wrong sometimes, and religions never admit that they change or that they get things wrong (you may occasionally hear "We were wrong then, but now we are right"). The idea that a religion is all good, absolutely correct, or the only correct religion is unjustified.
Many people want religion to tell them everything that they are allowed to do, or not allowed to do. When having an argument with a religious person, they will frequently justify a questionable act by citing the Bible or their Religion. According to Sartre, a religious person authorizes their religion to define their value set, and they are responsible for that decision. By accepting a religion we are authorizing that religion to command us as to what to do. By not accepting a religion entirely, or at all, we reserve the authority to specify our own value system. For this reason, I have not accepted a religion as "mine". It would be a great relief to say "I'm not responsible for my values, the church is", but just by saying that the church is responsible, you have decided to accept their values. By not accepting a religion, but still believing in God, I can have similar beliefs as a religious person (such as belief that God exists), however I am not restrained into accepting every aspect of a particular religion, and I am accepting the fact that I must decide what my values are and I am responsible for that decision.