Wikibooks
Wikibooks is a collection of open content textbooks. Open content means that these textbooks are freely available online. A textbook is defined by Wikibooks as "a manual of instruction or a standard book in any branch of study. They are produced according to the demand of educational institutions." Wikibooks is not... Wikibooks provides access to textbooks for these science/technology subjects: biology, computer science, engineering, mathematics, natural sciences, and physics.