The European Library (www.theeuropeanlibrary.org) is a website of the digital collections of 19 European National Libraries. This site gives opportunity to get  integrated access to the corporate sources of the European National Libraries.  You can search for digital and traditional documents free or in some instances for money.
       Some samples from the accessible things:
             - From the British National Library: 200 pictures from the two versions of the Gutenberg Bible
             - From the German National Library: digitised periodicals of the German Refugees Archives from 1933-1945
             - From the Portuguese National Library: manuscripts of the Portuguese writers from the 19th and 20th centuries 
             - From the Dutch National Library: works of the Netherlander painters before 1800

OCLC is a non-profit organisation, operating with participation of more than 40000 libraries from 76 countries. It was founded in 1967 by American Universities and it   brought in its online shared catalogised system soon. Its interlibrary-loan service has been operating since the end of ’70s. Basis of the services is the WorldCat database, that contains about 50 millions records and it increases with 4 items in every minute.