1. Project Gutenberg-

Project Gutenberg is a library of over 60000 e-books. Choose among free epub and Kindle E-books, download them or read them online.
Founder- Michael Hart
Founded- 1 December 1971
Special Feature- No fee or registration
2. Open Library-

At its heart, Open Library is a catalog. They have well over 20 million edition records online, provide access to 1.7 billion scanned versions of books, and link to external sources like Amazon.
Owner- Internet Archive
Founded- 2006
Special Feature- Provide access to all of Project Gutenberg’s books and thousands of others as well.
3. Internet Archive-

Internet Archive is a non profit digital library offering free universal access to books, movies and music, as well as 549 billion archived web pages.
Founded- May 1996
Where- San Francisco, USA
Special Feature- One of the world’s largest book digitalization project.
4. Many Books-

Many Book was established with a the vision to provide an extensive library of books on digital format for free on the Internet.
Founded- 2004
Special Feature- A platform where self publishing authors have the opportunity to introduce their work to the community.
5. Bookboon-

With over 75 million of downloads of our textbooks and business e-books every year, Bookboon is the largest publisher of e-books in the world.
Founder- Kristian and Thomas Buus Madsen
Founded- 1998
Special Feature- The textbooks and business e-books are available in many languages like, English, German, Dutch, French, etc.
6. Google eBookstore-

In the free section of the Google’s eBookstore, you can find bestsellers, classics and more. The books are available in different formats, and there are also ratings and reviews from other users to give you some handy pointers.
7. Free eBooks-

In short it offers a wide variety of books in various categories and each book is accompanied by reviews and reader ratings.
8. LibriVox-

LibriVox is an audiobook website. Its offers a wide range of audiobooks including classics and out-of-print books.
9. Hundred Zeroes-

Hundred zeroes is a collection of Kindle bestsellers that are now free. The books cover a large range of categories. You will need to use the free Kindle reader app to download and read these ebooks.
10. FreeBook Spot-

The website links free ebooks from other sites and you can download scientific, engineering, programming, fiction and many other subjects and topics from this site.
11. GetFreeEbooks-
GetFreeEBooks is a site that connects both author and readers in the world of free ebooks. Currently the site has more than 100 categories of free ebooks to read from.
12. Free TechBooks-

As the title implies this site lists free online computer science, engineering and programming books, textbooks and lecture notes, all of which are legally and freely available.
13. Scribd-

Scribd is the world’s largest digital library, where readers can discover books and written works of all kinds while publishers and authors can find an audience for their work. It is subscription based but you can get a week’s free trial.
14. EBooks-space-
Ebook-space covers topics such as Computer IT, Programming Language, Software Development, Tutorial, Database Design in PDF-CHM file format – strictly for the computer bods among us.
15. The Online Books Page-
The Online Books Page is designed to facilitate access to books that are freely readable over the Internet. It also aims to encourage the development of such online books, for the benefit and edification of all.