The Pre-Reformation Movements
A comprehensive presentation of the people and movements which anticipated the ideas of the Reformation: The Devotio Moderna (teachings of the Brethren of the Common Life), John Wycliffe and the Lollards, Jan Hus and also the Waldenses.
Roots of the Protestant Reformation
Part III of this site discusses the theological influences of Wycliffe, Hus and Erasmus on the later Reformers.
Wicliffe and His Times
Book 2 of Wylie's History of Protestantism, with an excellent history of Wycliffe and his influence on the Reformation.