Eric S. Raymond has another great post, this time on the story of Alan Turing. Raymond points out that today Turing is known more for his persecution of being a homosexual than for his actual accomplishments.
Indeed, Alan Turing was a great thinker. Though miss-credited with breaking the Germans Enigma machine (the Poles actually did it first, and the Americans broke the Japanese version second), he played a huge role in breaking German codes during World War II. Turing's contribution to modern computer science still plays out today, with the Turing Test being the still unattained goal of artificial intelligence.