My friends and family already know that I don't go to church and that I'm not religious, but I bet they have no idea that I am an atheist. My parents dropped by (without calling first) on their way home from church on Sunday and the first thing my mother did was pick up was a book I had laying on the table called "Raising Freethinkers - Parenting Beyond Belief." I don't think she looked at it long enough to really get the gist of what it was or if she did, she probably wouldn't want to believe that I am an atheist. You're brave for coming out and you will make new friends with common interests.
My full sympathy to you ): Inevitably, when you come out as an atheist you will probably lose one person close to you-but looks at it this way, if they would not tolerate your atheism they are probably people you would not want to be close to.