I highly recommend the Author Marketing Club to anyone who is aspiring to write a book or already has a book published that they wish to market.
Author Marketing Club has a number of resources that are free or low-cost to help “get the word out” regarding your book. There is a page for Kindle authors to submit free promotional days to several high-traffic websites. I have seen my promos double after listing on these sites.
Check them out at http://authormarketingclub.com.