The New York Times has an interesting set of audio interviews with scientists involved in the Manhattan Project, which took place from 1941-1946, resulting in the world's first atomic bomb. The scientists reflect on their feelings and what it was like to build such a powerful weapon.
Also on the NYT site is a nice video that traces the New York-based history of the Manhanttan Project. Interestingly, the project was originally called "The Laboratory for the Development of Substitute Materials." General Leslie R. Groves, who led the project, changed the name to "The Manhattan Engineer District," which he deemed less suspicious. In time, it simply became the Manhattan Project.