The European Union website -- EUROPA.eu -- contains information about the EU and its member states. Europa is available in 24 languages, although not all documents available from the site have been translated into all of these languages. The website lists member countries, EU institutions, EU activities by topic and links to EU treaties, legislation and jurisprudence.
The webpage of the Delegation of the European Union to the United States also contains a great deal of material about the European Union, including some very basic information about how the EU works and a downloadable EU Guide for Americans.
A Mabie Law Library research guide on European Union Law provides additional information about researching the European Union.
The Doe Library at the University of California Berkeley and the Green Library at Stanford University are both European Union Depository Libraries. They have large collections of EU materials which they make available to the general public. Government documents librarians at both libraries are also very knowledgeable about EU documents.