Internet History Sourcebooks Project
Fordham University: Medieval Sourcebook: Letter to the Archbishop of Mainz
Text of a letter written by Martin Luther to the Archbishop of Mainz in which Luther protests "the sale of indulgences to finance the building of a new cathedral."
Internet Encyclopedia of Philosophy
Internet Encyclopedia of Philosophy: Martin Luther (1483 1546)
An excellent biography of Martin Luther, concentrating on his philosophy and the background from which his ideas were obtained.