So I had a discussion with a friend of mine a while back about most things Christian in America. My friend is a doubter of evolution. I can't remember where the conversation started, but any time anyone doubts evolution, it really sets off my incredulity. One thing I asked him is how he thought science, Christianity, and atheism are related. He answered saying that atheism is the opposite of Chrisianity, and that science is the agenda of atheism (or words to that effect).
Now here's where a little semantics comes into play. I think the most popular definition/concept for "atheism" is a positive belief in the lack of a deity or deities. I don't think that's really the true spirit of atheism. For me, it's really the lack of belief in a deity of deities. I think I'm justified in that definition, though, because, etymologically speaking, I think that's really what it should mean anyway, agnosticism be damned.
At any rate, I think his response really set things straight as far as biases go. Reasonably, I think it can only be said that science is the pursuit of knowledge. Optimally, there'd be a lack of bias in any sense, not only religious, but political, personal, etc... Beyond a lack of belief in any religion, science and atheism really are separate and distinct.
As for atheism being the opposite of Christianity, by definition, I suppose the only true opposite of Christianity would have to be some kind of anti-Christianity, perhaps Satanism. If there were a Venn diagram of beliefs, atheism would have its own separate little circle away from the world's religions.
Another important topic we talked about was abiogenesis as distinguished from evolution. But that's for another time :)