Kindle Nation Daily has several highly effective campaigns available for promoting free and bargain books. In conjunction with Book Gorilla, it offers a reasonably priced, easy to submit and effective email service for book promotions. Their website hosts a section where authors are featured with their photo, books and links to Amazon. In the competitive book marketing realm, they're easy to work with and provide a reasonable return for the investment.
Twitter ID: @https://twitter.com/BookGorilla