This idea is discussed pretty early on in the Sequences; I always found that post to be one of the most compelling.
That essay strikes me as asserting that people can improve their thinking, but having very little detail about how, or about the process of getting over the psychological hump for those who are committed to the impossibility of improving their thinking rather than just ignorant of it.
Here's the easy idea-- how about a brochure about LW and SIAI? I was just at a couple of science fiction conventions, and it occurred to me that if there were a brochure, I could have printed it out and put it on the freebie table.
The hard idea is Sesame Street for rationalism-- entertaining video that dramatizes rationality. This would require money and possibly talents which aren't currently in the community, but I think a good bit of rationality could be dramatized, and it would be a big win for raising the rationality waterline.