Truly Good without God
I understand the recent billboard campaign promoting the idea that people can be “good without God” doesn't target fundamentalists, but I want to mention why I think it won't really have any effect on them whatsoever. No amount of personal virtue or charitable activity could ever convince most of them that you can live an ethical life without their religion. Beyond the issue of belief, which the campaign attempts to address directly, conservative believers have a very specific idea of what it means to be a good person. This includes refraining for all sorts of normal sexual activity, regularly attending and financially supporting a church in the community, and subscribing to and voting according to a conservative political ideology, at least on certain social issues. For some of them, it also means never drinking, smoking or dancing. Unless you act just like them in these matters, you'll never be good in their eyes. At most, you'll be slightly more tolerable.
The problem is that we can't honestly say that we act like strong believers even though we don't believe. We instead have to convince them the way we act isn't immoral because their objections to our lives have nothing to do with actual morality. That's a difficult task but a worthy one.