Directory of Open Access Journals (DOAJ), an online directory that indexes and provides access to high quality, open access, peer-reviewed journals at https://doaj.org/
Free ebooks by Project Gutenberg at https://www.gutenberg.org/
Google Scholar at https://scholar.google.co.in/
Internet Archive is a non-profit library of millions of free books, movies, software, music, and more at https://archive.org/index.php
Project MUSE: Online database of more than 200 journals from nonprofit publishers at https://muse.jhu.edu/
Shodhganga: a reservoir of Indian Theses at http://shodhganga.inflibnet.ac.in/
The Directory of Open Access Repositories – OpenDOAR at http://www.opendoar.org/