Enchanted Learning
http://www.enchantedlearning.com/Home.html

Enchanted Learning offers kid-friendly, curriculum-related information and activities on a wide variety of topics. Basic use is free. Schools and individuals may subscribe in order to access additional features.

World Book Online
http://www.worldbookonline.com

Every article from the 22-volume print set plus thousands more, with multimedia features, reviewed web sites and more.

CultureGrams
http://online.culturegrams.com

Up-to-date information about the cultural life of states and countries all around the world. Maps, photos, videos, slideshows and more.