One of the most worthwhile professional development experiences of my teaching career was the Facing History and Ourselves week long seminar. I attended it 13 years ago in Chicago and still use their teaching resources today.
Recently, I met the spouse of a colleague who told me that his grandmother had survived the Armenian Genocide. I peppered him with questions, but he admitted he didn't know much about it. So, I emailed him the PDF of their materials and he was very grateful. Finally, he could know the history behind his grandmother's sorrows.