The National Digital library of India (NDLI) is a project under Ministry of Human Resource Development, India. The objective is to collect and collate metadata and provide full text index from several national and international digital libraries, as well as other relevant sources. It is a digital repository containing textbooks, articles, videos, audio books, lectures, simulations, fiction and all other kinds of learning media. The NDLI provides free of cost access to many books in English and the Indian languages.

Directory of Open Access Books is a joint service of OAPEN, OpenEdition, CNRS and Aix-Marseille Université......

PDF Drive is your search engine for PDF files. As of today we have 82,144,730 eBooks for you to download for free. No annoying ads, no download limits, enjoy it......

An open textbook is a textbook licensed under an open copyright license, and made available online to be freely used by students, teachers and members of the public. 

Project Gutenberg is a library of over 60,000 free eBooks. Choose among free epub and Kindle eBooks, download them or read them online. You will find the world's great literature here, with focus on older works for which U.S. copyright has expired. Thousands of volunteers digitized and diligently proofread the eBooks, for enjoyment and education.....

ManyBooks was established in 2004 with the vision to provide an extensive library of books in digital format for free on the Internet. Many of the early eBooks are from the Project Gutenberg archives, which means you will be able to find a lot of classics on the site.

Internet Archive is a non-profit digital library offering free universal access to books, movies & music, as well as 439 billion archived web pages.

Open Library is an online project intended to create "one web page for every book ever published". Created by Aaron Swartz, Brewster Kahle, Alexis Rossi, Anand Chitipothu, and Rebecca Malamud, Open Library is a project of the Internet Archive, a nonprofit organization.

Library Genesis is a file-sharing website for scholarly journal articles, academic and general-interest books, images, comics, and magazines. In part, the site enables free access to content that is otherwise paywalled or not digitized elsewhere.

This website is launched in Jan 2018 as a free helpful source for all engineers. We are making great efforts to search for engineering books on the search engines and present free PDF kinds of these books here in one place with an easy way to download.

E-Books Directory is a daily growing list of links to freely accessible ebooks, documents and lecture notes found all over the internet. This website is now completely redesigned to be accessible to mobile devices with small screen sizes. The look is somewhat different now, but the content is the same. In this website exactly 10849 free e-books in 709 categories.

Z Library is the world's largest ebook Library. This Library has more than 5,181,055 eBoks and 77,518,212 + Articles.

The "Rare Book Room" site has been constructed as an educational site intended to allow the visitor to examine and read some of the great books of the world. Over the last decade, a company called "Octavo" digitally photographed some of the world ’s great books from some of the greatest libraries. 

LibriVox is a group of worldwide volunteers who read and record public domain texts creating free public domain audio-books for download from their website and other digital library hosting sites on the internet.

TradePub.pub established in 1994 as the first online subscription services provided for B2B magazine publishers, TradePub.com has grown to be the most sophisticated repository of content for professionals in over 33 industry verticals, with extensive reach through 1000's of B2B partner sites worldwide.  As the top destination for the latest research and publications, TradePub.com publishes curated resources on behalf of the world's largest and most influential companies.

The Universal Library Project, sometimes called the Million Books Project, was pioneered by Jaime Carbonell, Raj Reddy, Michael Shamos, Gloriana St Clair, and Robert Thibadeau of Carnegie Mellon University. The Governments of India, China, and Egypt are helping fund this effort through scanning facilities and personnel. The Internet Archive has contributed 100k books from the Kansas City Public Library along with servers to India. The Indian government scanned the appropriate books.