Martin Luther, 1483-1546, ministry began in 1517.
A history and some facts about Martin Luther can be found here: www.luther.de/en/index.html
Some of his works, translated into English, can be found here: Project Wittenberg (Martin Luther)
Martin Luther is the father of protestantism.
Martin Luther was an Augustinian monk, who began to challenge his superiors after he learned Greek and Hebrew (there were few contemporary translations back then) and found what he read in scripture to directly conflict with what the church taught.
In 1517 he wrote a letter to his superiors and included his now famous 95 theses (points). That link includes a photograph of the actual document. His 95 points however were aimed at a rather narrow point of theology. He was objecting to a practice known as Papal Indulgences, a practice where people could donate money to the Church, and receive a letter guaranteeing them their salvation.
Luther considered this a repulsive abuse of Church authority, and insisted that both those holding such indulgence letters and those handing them out (for money) were destined for hell.
The 95 points were a beginning, a first step at moving towards a Bible based theology, and away from the Church traditions of the day which were quite far removed from the Bible. Luther himself took many steps after that, and developed his own theology, which became the foundations of protestantism.
Luther was excomunicated by the Catholic church, but not declared a heretic outright (which would have conveyed a sentence of death by burning at the stake in those days) and spent many of his years as an exile. This state waffled back and forth as different political and religious forces ebbed and flowed.
Doctrinally, Luther is best known for teaching that salvation is by grace through faith. Consider that this simple doctrine had been absent from the church for over a thousand years.
Luther published his own translation of the New Testament in German, and it was very popular. Note that the first mass printed Bible, the Gutenberg Bible predates Luther's efforts by almost a hundred years. The Gutenberg Bible was also a german translation and appeared in 1454-1455, and was named after its printer Yohann Gutenberg.
Luther's greatest contribution of all is possibly that he restored the idea that scripture is the keeper of truth. Thus undoing over a thousand years of false teaching that the Catholic Church was God's ordained keeper of truth (thus they could and did overrule scripture by via papal edict, or as Jesus would have said, traditions of men). Sadly, the Catholic church maintains this teaching to this day.
Luther lived long enough to see the reformation take hold and grow like wildfire. It persevered as the faithful philadelphian Church for almost 300 years before the trend towards apostacy became ireversible in the mid 1800's under Charles Finney, which marks the birth of the Laodicean church that is in full bloom today.
There are many false myths about Luther.
Luther was not perfect, he was anti-semitic for example. And some bits of Romanism remained in his thinking, but tiptoe around those and the rest of what he had to say is quite interesting.
Luther was essentially what we would call Calvinistic in his writings (although he predates Calvin by a few decades), writing that true saving faith was created in us by God, and is not something we can work up on our own. In his commentary on Galatians 1:4 he condemns talk of free will (that we can come to God on our own) as a filthy rag.
See Martin Luther's Definition of Faith
In other doctrinal matters Luther wrote against the celibacy of the priesthood among other things.
As I read more of Luther, I find him to be an excellent teacher who covers the basics of the Christian faith, although you have to weed through the remnants of Catholicism that remain in his thinking. In history I believe he would have been the first of his age to really focus on basic Christian doctrines, as pre-reformation theology was bound up in every sort of false teaching.
Much of what Luther wrote was aimed at being read by laity, he goes through basic Christian teachings carefully and clearly. It is both exciting and humbling to hear the clear truths of the Bible proclaimed by one so revered in history as Martin Luther.
May I suggest that as an alternative to the latest devotional from your local Bible bookstore that you bring a copy of one of Luther's writings to your next Bible study.