Internet Public Library ( IPL ) is a great resouce for educators. It has a wealth of knowledge organized by topic. It also provides special collections, magazines and newspapers.
2- Awesome Library
This is another great online library that provides directories, text books, documents and many more. It has a user friendly interface and is very simple to browse.
3- Library of Congress
4- Public Libraries
5- Free Classic Reader
6- WorldCat
WorldCat helps you find a library near you. It actually connects you to the collections and services of more than 10.000 libraries worldwide.
7- Questia
8- Library Spot
9- Free Internet Libraries