bike magazines can also spread the ss love. dirtrag is all about single speeds and 29"ers as well as lightly covers fixies on the road as well as dirt. i also think bike builders/companies help get the word out by building new models around those more "unconventional" bike ideas...

mostly though, i really think your local biking community has the biggest impact... especially when they see it in action. cycling is pretty huge here; lots of riders know what a fixie is or notice a single speed on the trail... but when they see someone doing it, interacting in their same environment, it helps push them that much further to try it or at least consider why someone wouldn't want suspension or gears or coasting or whatever. i think it's that real world experience that really puts the sparkle in their eye, rather than looking at some picture in a catalog/magazine/website/dumptruck/etc.