Here are a few places where you can find free ebooks:
Project Gutenberg offers over 39,000 free eBooks compatible with several devices. Download them or read them online. The original and still probably the best.
ManyBooks offers over 29,000 free eBooks compatible with several devices. The site offers a wide range of genres, both fiction and nonfiction.
GoodReads the largest site for readers and book recommendations in the world. The site offers several eBooks available for download.
Planet eBook offers free classic literature eBooks available for download.
Smashwords features a collection of free books from indie authors and publishers; this site does contain mature content.
Librarything offers a variety of free eBooks and a way to catalog your books.
Bartleby Publisher of literature, reference and verse.
E-Books Directory Lots of free eBooks and they often have a “book of the month”.
Google Books Some are free, some are pay.
Open Library People can read books and add books to this website.
Sciyo This has scientific books and papers available for free.
Ereader News Today Tips, tricks, bargain & free books for your Kindle or Kindle app.
Please, if you know of any other websites and/or blogs that feature free ebooks, email me and I will add them here.