The Europa provides an overview of economic and monetary union:
https://ec.europa.eu/info/business-economy-euro/economic-and-fiscal-policy-coordination/economic-and-monetary-union_en
The European Commission provides further detailed and up-to-date information and commentary on Business, Economy and the Euro at the following link:
https://ec.europa.eu/info/business-economy-euro_en
The European Commission’s DG for Economic and Financial Affairs is a good source of information on economic and financial policy in general: https://ec.europa.eu/info/departments/economic-and-financial-affairs_en
The Europa website provides an overview of the history of Economic and Monetary Union:
https://www.europarl.europa.eu/factsheets/en/sheet/79/history-of-economic-and-monetary-union
The ECOFIN Council of Ministers is one of the most active configurations of the Council of the EU. Its website contains links to press releases, documents and meeting schedules: http://www.consilium.europa.eu/policiesold/council-configurations/economic-and-financial-affairs?lang=en
The European Central Bank (ECB) controls monetary policy for the Eurozone countries. Its website contains an overview of the role and organisation of the bank, as well as statistics and convergence reports:
The Treaty on Stability, Coordination and Governance in the Economic and Monetary Union can be accessed here:
http://european-council.europa.eu/media/639235/st00tscg26_en12.pdf
Information on the European Banking Union (EBU) can be accessed here: https://ec.europa.eu/info/business-economy-euro/banking-and-finance/banking-union_en