US National Archives
Nara: The Marshall Plan
This National Archives and Records Administration site contains a brief definition of the Plan and has a picture of Marshall. There also are links to a couple pages of the Economic Cooperation Act.
Smithsonian Institution
National Portrait Gallery: George Marshall
This is a brief but informative piece on George C. Marshall - creator of the Marshall Plan. Includes pictures of most of the world players at the time. Describes his role in formulating the Marshall Plan.