If you have a free ebook and you want to get downloads, you should submit it to http://www.getfreeebooks.com/?paged=2. The numbers don’t lie. Two days ago they posted my submission for my comic sci-fi story ‘The New Guy in Moon Base Twelve‘ and just look at the chart:
I had a similar experience with my allegorical Zombie Nights a couple of years ago. In that case, the good folks on that website happened to go on a two month vacation the day they posted it, so it remained on the front page through the first two months of summer. As a result, it became one of Smashwords’ most downloaded ebooks ever, and is probably the main reason why any of my books have received any attention at all. I can’t guarantee they’ll go on vacation when they post your free ebook, but it’s free and easy to submit, there are no strings attached, and they seem to attract a large audience.