Amazon is certainly my favorite online place to shop, but as a devoted bibliophile I have to tell you there are other places that offer free books too.
Barnes and Noble is a great example. While you may not be able to use their electronic books on your Kindle (they sell the Nook, thankyouverymuch), you can certainly download their free software and use it on your PC, iPhone, iPad or Android. I have noticed several occasions when they had something available for free that Amazon did not (and vice versa).
Inkmesh is a great website that keeps track of just this sort of information, so you don't need to go hunting on your own. They always have the most current free eBooks available, with convenient links to where you can get them. They do keep track of Amazon freebies, but offer several others too. If a book is available at more than one outlet, there will be links to all of them. You get to choose, and that is good.
And you thought I just pulled these out of thin air?
Enjoy, dear readers!