I know I've gone on and on about Smashwords, but here's another bonus to becoming a free member of the site - you can become an affiliate, and market eBooks on your blog, website, Twitter, or Facebook! That includes my very own book, Twin Rivers.
How much you earn depends on how much the book is selling for, and how many books you sell. I have it set that you earn 11% of my book price for every one of my eBooks that you sell - not too bad!
Here's a link to find out more about Smashwords' Affilitate Program.