European Union Research: A Beginner's Guide: Getting Started

These sites have good background about the EU and its legal system.

• Europa - Gateway to the European Union - For background, look at About the EU. The EU by topic, and EU institutions and bodies sections are also very helpful. The Your Europe portal is a great first online stop if you are looking for information about how the law protects rights and impacts many aspects of daily life in EU member states.  The EU created this site to “help you do things in other European countries,” including “moving, living, studying, working or simply travelling[.]” 
• Europa's EU Law page - Brief summaries of major types of law and processes.
• EU Guide for Americans - See especially Chapter 2, "How Is the EU Run?" (This Guide for Americans is a 45-page PDF document by the European Union Delegation to the United States.)
• Europeana – a portal providing centralized access to legal and other cultural resources from digital collections of thousands of cultural institutions across Europe. Funded by the European Union, and via collective efforts of 37 aggregators, Europeana currently retains over 50 million cultural items in textual, photographic, and/or audio/visual formats.

These are sites for the European Union as a whole, for some of its constituent bodies, and for its laws and legislation.

• Council of the European Union

  The Council has a major role in enacting EU legislation. The Council is sometimes also called the "Council of Ministers."

• European Parliament

  The EU's only directly-elected body. It shares legislative powers with the Council of the EU.

• European Commission

  The Commission's roles include initiating and drafting proposed EU legislation. Its Green Papers and White Papers are helpful if you are researching the background of EU legislation. Prelex can help you research legislation and decisions under consideration.

• European Council

  Not the same as the Council of the EU. The European Council has no legislative powers. Made up of the heads of state or government of every EU country, the Commission President and the European Council President, The European Council "defines the EU's overall political direction and priorities .... and sets the EU's policy agenda."

• European Central Bank

  The ECB site's Legal Framework section includes EU legislation relating to the bank as well as ECB legal acts.

• EUR-Lex - Access to European Law

  Free access to European Union law: directives, regulations, decisions, etc. Includes the Official Journal of the European Union. Also includes EU treaties and international agreements.

• Curia - Court of Justice of the European Union

  Information about and decisions from the Court of Justice and the General Court, and case law from 1954 to the present. (Eur-Lex also has access to case law from 1954 to the present.)

Westlaw has extensive collections of European legal materials. 

• European Union sources - Westlaw

  Note especially the categories for Cases and Legislation.

Lexis's EU materials are available via the "International" tab in the "Explore Content" section of Lexis Advance.

• European Union sources - Lexis

  Includes EU cases and EU "statutes" and legislation (which includes treaties).