Graffiti artist JR had a very difficult task when invited to talk at TED conference: to change the world. He obviously couldn't do it, but in my point of view, he helped a lot of people to see it in a different angle. And all he needed was a camera, a printer and some glue. He posted giant portraits from people going through political or social problems in the streets and slums of Rio, Liberia, india, France. His project Womens are Heroes (previously posted here) shocked Brazil and made the whole world aware of horrible atrocities Brazilian police were doing at the favelas.
You can change or own image here, so he can glue it. Beautiful project!