National Geographics Maps:

Illustrating the world around us through the art and science of mapmaking.

Britannica:
An online encyclopedia from Encyclopaedia Britannica with hundreds of thousands of articles, biographies, videos, images, and Web sites.
Source: Britannica

Refdesk.com:
A free and family-friendly web site that indexes and reviews quality, credible, and current web-based resources.
Source: Refdesk.com

Infoplease.com:
A factual information on an array of topics, including current events, pop culture, science, government.

Crash Course in Copyright:
From the University of Texas, all you need to know about copyright.