BookBub where you can search for e-books for your kindle from Amazon (Apple, Google and Kobo are available also). They send daily emails with books that you might find interesting depending on the genres you have chosen when you sign up with them.
You won't believe how many books I have snagged this way and the bonus is that a lot of them are freebies. In fact I have so many books to read on my kindle now I don't think I will ever get through them all.
I also use Goodreads to find great books to add to my already large To Read list. If you use Goodreads and wish to add a friend you can find my profile HERE.