I think works of fiction are the most effective way of spreading the word (logic and rationality). Personally, if it hadn't been for being exposed to rationalism from science fiction at an early age, I doubt I'd have ever come to this site.
Anyone who reads science fiction is probably already going to be reasonably receptive to our ideas; what would really make a difference would be promoting rationality in other genres of fiction.
This has been discussed some, but I don't think it's been the sole subject of a top-level post. I want to find out other people's ideas rather than driving the discussion into my ideas, so I'm asking the question in a very general form, and holding off on my own answers: