Links
Data on compliance with EU law
Internal Market Scoreboards (DG Internal Market, European Commission)
Infringement Procedures (DG Internal Market, European Commission)
Enforcing EU Law (Secretariat General of the European Commission)
Eur-lex (Access to European Union Law. Includes access to notified national transposition measures)
Often used data sources
Governance
World Bank Governance Data
Internet Center for Corruption Research
IMD World Competitiveness Yearbook
Institutions
Political Constraint Index (Henisz)
Polity IV Project: Political Regime Characteristics and Transitions, 1800-2008
Veto Players Data (Tsebelis)
Regional Authorities Data (Marks, Hooghe and Schakel)
Party positions
Chapel Hill Surveys on Party Positions
Party Policy in Modern Democracies (Benoit and Laver expert survey)
Comparative Manifestos Project (party positions)
Decision Making in the European Union (policy positions)
Public opinion
Eurobarometer
European Social Survey
Economic data
Other
Databse of national labour law NATLEX