How have I not seen this sooner?
It all started when John Maloof attended an auction while researching a history book on Chicago. He bid on - and won - a lot consisting of thousands upon thousands of negatives, having no idea what was on them. They turned out to be the work of one Vivian Maier. She was an immensely talented photographer, and the collection contains some of the most amazing 1950s street photography I've ever seen. It's especially incredible when you remember that this was long before digital photography - film was precious, so each one of these pictures was carefully framed, timed and shot individually.
John Maloof has put together a blog in tribute to Vivian, and I believe is working on producing a book of her work.