When and how to come out as poly to friends and coworkers is something that I'm wondering about too. How do you bring the subject of open marriages up? I have a couple women friends with whom I'd like to tell about my open relationship. I'd ask them out, but I wouldn't want them thinking that I'm cheating. I would keep my poly a secret and stick to women I meet online, but the women I've met in person are much more interesting to me and have more in common with me.
As for coming out as poly to a religious family, I'd just let them be. The athiesm thing was probably hard enough on them. Introduce them to one boyfriend and if they have to meet one of your other partners for any reason, just tell them that he or she is a friend. They don't need to know the intimate details of your sex life.