That's what forums like this are good for, letting you discuss your beliefs with people of like (and unlike) mind. If your friends are willing to remain friends while not broaching the subject of religion with you, they're doing better than a lot of people do when they learn a friend or family member is an atheist. Don't throw the baby out with the bathwater. If opportunities to discuss it come up, take them. But if your friends are uncomfortable with it, don't force it. Most important, be comfortable with who and what you are, and I think your friends may be forced to deal with some uncomfortable questions of their own.
"Well, evolution is a theory. It is also a fact. And facts and theories are different things, not rungs in a hierarchy of increasing certainty. Facts are the world's data. Theories are structures of ideas that explain and interpret facts. Facts don't go away when scientists debate rival theories to explain them. Einstein's theory of gravitation replaced Newton's in this century, but apples didn't suspend themselves in midair, pending the outcome. And humans evolved from ape- like ancestors whether they did so by Darwin's proposed mechanism or by some other yet to be discovered."
-Stephen Jay Gould
-Stephen Jay Gould