There are several facebook pages dedicated to selling Kindle and Nook books. Search for these sites, become a part of the community and make sure you know the rules. Some pages let you post about your book once a day. Other pages you have to the administration about your book and then they will post it for you. An example of these pages is Authors on the Cheap and Free Books for Kindle. It’s probably best to check these pages once a day, but I don’t have that kind of time. I usually try to pop in at least once a week.
I can not stress how important sites like these are. If you want to sell your ebook, you need to go where the ebook readers are. These sites have thousands of them and you can tell them about your book for FREE! You can't beat that.