Monday, July 14, 2014 (Bastille Day) is the first digital book day, according to DigitalBookDay.com. It is intended to be a “day to celebrate readers, stories, and the authors who create them.” The site is offering links to over 400 free books on hosted various sites. There is a wide range of genres represented: historical, romance, science-fiction, fantasy, mystery, non-fiction, thrillers, and young adult. Represented are books from authors from around the world, including C.J. Lyons, Bob Mayer, Linda Welch and many, many more.
PLEASE NOTE: The book links will not be live until July 14, 2014. Without being able to click through, it was not clear to me what format the free books are being offered in (mobi, epub or PDF).
There is also a link on the site to sign up to be notified of future free digital book events.
Update: The Digital Book Day site seems to be down. I am getting a database connection error.
Update 2: Evidently, the server crashed. There is a post here on Google plus where authors have been invited to post links to their free books. Authors are welcome to post links to their free books below in the comments.