Our Bookshelf Favorite 

"Our Bookshelf is a social network where people can share their
ebooks as easily as they can share print books. At the moment, most
copyrighted ebooks don't allow you to share them. This is because when
you buy an ebook you don't own the book the way you own a print book.
You own a license to read it on certain devices and most of these
licenses prohibit sharing. We plan to create a new license that does
allow sharing, but in a way that treats authors and publishers fairly.
This is a huge undertaking that your contribution will help make
possible. We will start by creating a social network for sharing public
domain ebooks. These ebooks are not
copyrighted so users can share them freely. A lot of great books are in
the public domain, including most classics. True you can find some of
them elsewhere, but learning about them through your friends can
introduce you to books you might not have known about or overlooked." (From site.)