"...I grasped that the justice of God is that righteousness by which through grace and sheer mercy God justifies us through faith. Thereupon I felt myself to be reborn and to have gone through open doors into paradise."
The 95 Theses that started it all on October 31, 1517.
Stand to Reason's blog has a nice summary of Luther's role in the reformation.
Today only: Reformation Study Bible for $15.17 @ Ligonier Sorry, they're already sold out. I didn't get mine either :(
Here are some Reformation Day sermons from Reforming my Mind
Addition: The Reformation Day Symposium at Challies