• Directory of Open Access Books (DOAB) -Provides an access to over 3000 e-books from more than 100 well-known publishers covering almost all disciplines.
• PDF Drive is a free search engine which allows you to search, preview ,download millions of e-books
• Million Book Project : A digitization project of books initiated by Carnegie Mellon University. It provides access to over 1.5 million e-books to the readers.
• Many Books is an extensive library of books in digital format for free on the Internet
• Getfreebooks brings both authors and readers into the world of free legal ebooks
• The world's largest ebook library.
• ebooks of an Indian Writer in English 10 free ebooks
• Free Book centre contains links to thousands of free online technical books.
• Free ebooks in different categories. Category's range from business, art, computing and education.
• The OAPEN Library contains freely accessible academic books, mainly in the area of humanities and etc.
• Google books the world's most comprehensive index of full-text books
• SpringerOpen books
• Full Text Publication
• More than 3,000 Open Access ebooks are now available at no cost to libraries or users. These titles reflect JSTOR’s high standards for quality content and are freely available for anyone in the world to use.
• e-books directory 10,173 Books
• InTech open Books
• Project Gutenberg
• Read Print
• The Universal Digital Library Million Book Collection
• Indian Author Books
• The Complete Works of William Shakespeare

Open Text Books

• A collaborative collection of twenty-nine educational non-profit and for-profit organizations which are affiliated with more than 200 colleges.
• Open Access Textbooks is  a FIPSE Grant Project to creating a model of open textbook and establish a state wide open textbook initiative.
• This is an open access textbook publishing initiative established by State University of New York libraries and supported by SUNY Innovative Instruction Technology Grants.
• Open Textbook Library hosted by the University of Minnesota. It covers over 160 college-level textbooks with an emphasis on Science and related fields.
• Virtual textbook of organic chemistry provides fully operational organic chemistry textbook, divided into the two overarching topics of General Principles and Functional Group Reactions.
• Boundless.com offers the textbooks and readding materials on chemistry.
• Saylor.org Bookshelf
• E-Books Directory
• Techbook
• Project Madurai
• NCERT Books

Audio Books

• Read Without Limits Enjoy an unlimited number of books, audiobooks, magazines, and more.
• Agenda Web (100)
• Audio book Treasury
• Books Should Be Free (7,000)
• Educational Technology Clearinghouse (about 200 audio books)
• Free Classic Audiobooks (100+audio books)
• Gandhi Autobiography
• Learn Out Loud (3000)
• Librivox (9,000+audiobooks)
• Lit 2 Go
• Naropa Poetics Audio Archives (817)
• Podio Books (1000+)
• Project Gutenberg – ebooks (2000+audio books)
• Spoken Alexandria Project
• Storynory (Several hundreds of audio books)
• The Internet Archive (9,954)
• Thought Audio
• Voices in the Dark

Tamil Books

• தமிழ் இணையக் கல்விக்கழகம் - TAMIL VIRTUAL ACADEMY
• இணைய தமிழ் நூலகம்
• செந்தமிழ்
• Veettuku oru Noolgam
• Free Tamil Books, Tamil PDF ebooks and ePub Tamil collection for download online
• Balakumaran Stories
• https://poovascollections.blogspot.com/p/balakumaran-stories-pdf-free-download.html
• Arignar Varalaru

Rare Books

• Indian Rare Books
• Rare Books – 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.