Wikijunior

http://en.wikibooks.org/wiki/Wikijunior

The aim of this project is to produce age-appropriate non-fiction books for youth from birth to age 12. These books are richly illustrated with photographs, diagrams, sketches, and original drawings. 

Discovery and Innovation

The Elements — Fun Science Experiments — How Things Work

The Natural World

Big Cats — Biology — Bugs — Dinosaurs — Human Body — Solar System

Our World of People

Ancient Civilizations — Kings and Queens of England — Languages — United States Charters of Freedom — World War II — World at Work

Geography

Europe — South America — World Heritage Sites

School Time

Geometry for Elementary School

Pre-readers

Alphabet — Animal Alphabet — Colors — Flower Alphabet — Food Alphabet — Numbers from 1 to 20 — Small Numbers — Maze & Drawing Book