Word-of-mouth, Facebook page, Twitter, various online communities I'm a part of. Part of the challenge is being "always on" and believing in my product (my book) and passing that belief on to other people. The way to look at it, I think, is that every person I don't mention it to ends up being a potentially lost sale.

I'm also looking into advertising on Something Awful. I'm exploring Facebook ads, but I'm not sure how good they would be. Google Adsense would be nice, but I was banned from the Adsense/Adwords service some time ago for some reason and Google has been especially unhelpful about responding to anything about any of their services.