Wikipedia: Manhattan Project
Hyperlinked history of the effort during World War II to develop the first nuclear weapons by the United States with assistance from the United Kingdom and Canada.
Fifty Years from Trinity
On July 16, 1945, the date of the first atomic explosion, everything changed forever.
Documents, photographs, and other materials drawn from a cultural history of the Manhattan Project.
Nuclear Files.org: The Manhattan Project
Featuring historical documents, interviews, and conversations which help illustrate the history of the Manhattan Project.