Even if you don't know her story or her name, you know at least one of Diane Arbus' haunting images. Her portraits are intensely intimate due in large part to the medium format camera she used, which allowed her to be face to face with her subjects and her gentle and seductive nature that made people feel at ease.
She often and almost exclusively chose outsiders and the forgotten to photograph and this choice has lead to much controversy about her career. Since some of her subjects are handicapped in some way, many of her detractors say she was exploitive, a claim I do not agree with (and neither does Todd Solondz another artist who focuses on outsiders and the grotesque in his work).
There was a huge retrospective of her work at the Met in 2005 and some of her photographs hang in their permanent collection. You can find them in the collections of the Museum of Contemporary Photography in Chicago and at the International Center for Photography in New York, among other museums and libraries.
She took her own life in 1971 by overdosing and slitting her wrists and took with her a singular talent.