Theories of EU Governance

POLITICO is a global, non-partisan politics and policy news organisation, and an influential publication on European Affairs. It publishes up-to-date news and analysis on a range of issues related to governance in the EU, which can be found under the ‘EU Governance’ tag on its website:
https://www.politico.eu/tag/eu-governance/.

Established in 1983, The Centre for European Policy Studies (CEPS) is an independent, Brussels-based think tank which undertakes research on European affairs, publishes reports and working papers and provides a forum for European policy debates.
https://www.ceps.eu/about-ceps

The Institute of International & European Affairs (IIEA) is an Irish think tank which produces briefings, reports and publications in all areas of European Affairs, in general, and on issues pertaining to European integration and governance, in particular. 
https://www.iiea.com/

ARENA is a multidisciplinary centre of basic research at the University of Oslo, studying the evolving European political order. The centre publishes an online working paper series which includes work on EU governance.
http://www.sv.uio.no/arena/english/research/publications/arena-publications/workingpapers/

The Journal of European Public Policy is a good source of articles on policy networks, and new institutional approaches.
http://www.tandfonline.com/loi/rjpp20#.VDvr6vldW4g 

The Journal of Common Market Studies publishes a wide range of articles related to European integration.
http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1468-5965

The European Integration Online Papers was an online peer-reviewed journal which published research related to European integration. It was published by the European Community Studies Association, Austria, and is archived at:
eiop.or.at/eiop/