Glenn Reynolds links to an article on oral histories. In 8th grade, my son had to do an oral history of someone in my family. I bought him an mp3 recorder, one of those little dictation things they sell at Staples or Office Depot, and he recorded about 4 hours of interviews.
My dad passed away last week, but due to dementia lost the ability to discuss his life long before that. My dad had an amazing life, growing up in a tiny house in Depression-era Iowa and eventually running one of the largest corporations in the world. He never talked about himself. Knowing him, one couldn't imagine him writing a memoir. In a day where executives hire PR agents to puff them up in the press, my dad scoffed and derided the practice. He bought all his casual clothes at Sears until his teenage daughters made him stop.
So the only history we have of him in his own words wouldn't exist if a wonderful teacher hadn't assigned him the project.