Reformation, also called Protestant Reformation, the religious revolution that took place in the Western church in the 16th century. Its greatest leaders undoubtedly were Martin Luther and John Calvin.
Introduction to the Protestant Reformation. A lesson from Khan Academy including videos on a variety of aspects of the Reformation.
Martin Luther as Priest, Heretic, and Outlaw. This article describes Luther and his writings, and the conflicts with the Church. Includes many images of documents from the time.
The Protestant Reformation. National Geographic provides a history of the Reformation, with reference to its effects around the world.