Chrome extension notifies users when books are available for free as E-books/Audiobooks [i'm the designer] : books
"Who's ready to save some money on books?! I created an app that I think r/books will be interested in. Mockingbird Freebooks is a Chrome extension that will notify you when the book on the current page is available for free download as an E-book/Audiobook. The app integrates with Project Gutenberg, a non-profit that makes books in the public domain available for free download via their website. Whenever a match is found, a pop-up will appear with a link to the download page. You can download the app here from our website getmockingbird.com and the Chrome Web Store. Currently, it only works when shopping on Amazon, but I am planning on adding support for Barnes & Noble and other online retailers. The app is in its early stages, so please let me know any questions/feedback!! ..."