My conclusion, based off of the previous posts and my own stores of knowledge, is this:
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We would certainly not be where we are now without religion. Artisticly, socialy, and moraly we would not be like this. Society might have not even evolved as qiuckly, or it might have done so and evolved completely differently. Eventually someone would create a religion. Assuming our knowledge of science would be limited, people would need to explain things. They also need a source of comfort, security, inspiration, and purpose. Religion offers all that. They also need some type of control, or a saftey net to fall back on, and a god can do all that. Looking at the way we are, a world without religion would probably be impossible.

As for religious prejiduce/crusades/oppression, it wouldn't happen for religious reasons, it would be limited to race, gender, political views, ect. (We wouldn't have religious terrorism, terrorism would happen for different reasons.) There wouldn't be any religious charity organizations, people would just do it out of care and compassion for their fellows. Our history might be less bloody though, no religious wars or persecutions. Slavery might not have been abolished at all, or it would have taken a far longer time to do so. Many cultures would have been considerably duller and some great works of art and architecture might never have been created. Parts of the map might not yet be filled in or not be filled in that quickly, and communtication/diffusion between cultures wouldn't have taken place on a very large scale. The population of earth would probably be a lot larger since no one was killed in the name of religion, (ex: religious wars, persecutions, sacrifices...) then it would decrease drastically because all the resources on the planet wouldn't be able to serve such a great number of people.