One of my favourite teachers ever was my sociology tutor in college. He was a tiny polish man brimming with passion and a palpable energy that was infectious. He used to say to me "Question everything, it's good for you. Always ask whose agenda am I being fed?" I never missed his classes, he was inspirational. In light of this, I thought a good deed would be to write a letter to a teacher you felt had a strong impact on you, thanking them for their encouragement and support. If you can track them down, in most cases I tink they'd be delighted and somewhat touched.