Links of Free Electronic Resources (available on public domain)
Encyclopedia.Com
Encyclopedia.com offers millions of free articles, pictures, facts, and biographies along with information about topics like the arts, science, sports, medicine, accounting, and management. Encyclopedia.com is an ideal online reference source for researchers, students, educators, and professionals alike.
http://www.encyclopedia.com/

Project Gutenberg
Project Gutenberg offers over 46,000 high quality free e-books: choose among free e-pub books, free kindle books, download them or read them online.
https://www.gutenberg.org/

Open Library
Open Library project is making thousands of library records freely available for anyone's use.
https://openlibrary.org/

We Give Books
Beautiful stories for children and beginners. (registration required)
http://www.wegivebooks.org/

DOAJ (Directory of Open Access Journals)
DOAJ is an online directory that indexes and provides access to quality open access, peer-reviewed journals.
http://doaj.org/

Arabic Collections Online (ACO)
ACO is a publicly available digital library of public domain Arabic language content. ACO currently provides digital access to 11,566 volumes across 6,820 subjects drawn from rich Arabic collections of distinguished research libraries.
http://dlib.nyu.edu/aco/