The Europa website provides a historical overview of the period 1945-1959: http://europa.eu/abc/history/1945-1959/index_en.htm
The Europa website also contains information and multimedia resources related to the founding fathers of the EU:
The Virtual Resource Centre for Knowledge about Europe (CVCE) is a resource centre for the study of the EU. It contains links to multimedia resources relating to the history of European integration, including media clips of key historical events: http://www.cvce.eu/home
The Marshall Foundation provides background materials and the text of George Marshall's Harvard speech of 5 June 1947, in which he set out the design of the Marshall Plan for the reconstruction of Europe. The site also provides links to interviews, films, videos and timelines.
The Organisation for Economic Cooperation and Development (OECD) is the successor to the OEEC. Its website contains some information on the history of the OEEC. http://www.oecd.org/document/48/0,3343,en_2649_201185_1876912_1_1_1_1,00.html
La Fondation Robert Schuman contains information on Robert Schuman and the Schuman Declaration of May 1950 which set out a blueprint for the European Coal and Steel Communities (ECSC).
The website of the Jean Monnet Foundation contains a range of different written and oral resources, including excerpts from Jean Monnet's memoirs describing the construction of Europe.
The British Pathé website contains archive news reel footage covering key episodes in the history of the EU, including the founding of the ECSC and the EEC. https://www.britishpathe.com/workspaces/page/the-european-union