Thanks for the blog articles. I hadn't tried Goodreads ads yet, so I decided to give one a spin. I've done Facebook ads, but only when Facebook gave me a $50 credit to use for advertising!
Posting a weekly "ad" on the Amazon Kindle and nook Facebook walls helps, but what helps more is chatting it up with people on a regular basis. The Kindle fan page has over a half-million fans -- that's a lot of potential readers! Of course, only a few hundred or thousand will see your post before it scrolls off the screen -- and often the same people that saw it last time!
I've tried KND, too. The first time, I made a few bucks over the cost of the ad. The second time, I didn't even break even. If the readership were growing, I'd consider it again, but in the last six months, Steve hasn't reported a large increase in the number of readers, especially considering the Kindle fan page on Facebook grew 5-fold in that time. That and the fact that his price has gone up for the sponsorships makes it not viable for the genres I write. If my books had a wider appeal, maybe.
I've also tried the Kindleboards book-of-the-day and the banner ads and got poor results. I won't try forum ads again, unless they were targeted at my reader (such as sffworld.com, except those readers don't tend to like indies).