Open Access Digital Libraries

National Digital Library (NDL) - A virtual repository of learning resources containing textbooks, articles, videos, audiobooks, lectures, simulations, fiction, and all other kinds of learning media for the learners/users community. 

World Digital Library - 

Uttar Pradesh Higher Education Digital Library

Internet Archive Digital Library - Internet Archive is a non-profit library of millions of free books, movies, software, music, websites, and more.

Z-Library Project - The world's largest ebook library.

PDF Drive - Millions of ebooks.

Project Gutenberg - Project Gutenberg is an online library of free eBooks.