These free books can be downloaded onto a Kindle device, or onto a phone or tablet to use with the free Kindle app.
Sometimes these books are only free for a few weeks, so check carefully. These lists contain fiction and non-fiction. Some are adult themes, so please don't download them unless you're 18 or over.
New Free Kindle Books for Teen and Young Adults: http://newfreekindlebooks.com/free-young-adult-kindle-books/
Baen.com: Free Library: http://www.baen.com/categories/free-library.html
ManyBooks: Over 33,000 free ebooks. http://manybooks.net/
DigiLibraries.com: http://digilibraries.com/
Amazon.com has some free Kindle books: LINK to "top 100 free"
Scroll Down on this site and you will see TONS of links to free books and series.