Everyone has a list of free stuff from Amazon for the Kindle. It's all the same. Sometimes they don't even tell you why you need the items. They also don't list other places you can go for free things that can be read on Kindle, on your PC, and any other reader. Sometimes you can even find those same items that are .99 cents to 9.99 on Amazon for Kindle on other websites for free. Here is a list of my favorites that must be had and completely free and legal.
1. Brave New World-Aldous Huxley
This can be found for free in multiple formats from the banned books section on archive.org. Simply pick your format from the menu to the left, download to your computer, and upload to your reader. On Amazon, this book is 4.79 for the Kindle. http://www.archive.org/details/Book-AldousHuxley-BraveNewWorldPdf
This one is only .95 cents from Amazon, but still, if you can save .95 cents, why not, right? From the same website through the banned books section, you can download it for free, with other works by Voltaire and introduction and notes. http://www.archive.org/details/candideotherroma00voltuoft
3. Where Angels Fear to Tread-E. M. Forster
Only .80cents on Amazon for Kindle and the free Kindle software for iphone, etc., this can be had for free at http://www.archive.org/details/whereangelsfeart00forsuoft
4. The Art of Caricaturing-Mitchell Smith
I downloaded this for free for the little artist at my house. On Amazon, it's 3.99 for Kindle. http://www.archive.org/details/artofcaricaturin006061mbp
5. And my favorite new find: type this into your Kindle web browser if you have the version that has the browser http://m.gutenberg.org or go to http://www.gutenberg.org/wiki/main_page
on your computer and download a lot of ebooks categorized by genre, author, title, subject, most popular, and language. They download quickly from the Kindle on the mobile version of the site and go right to your home page. There are a few extra pages about the Gutenberg project and some disclaimers at the beginning of the books, otherwise, they are the same as the Kindle versions that I've seen, and open right to the last page you were on, just like the Kindle books.