A shameless plug:
The Center for Applied Policy Research, a think tank attached to the University of Munich does good work on the nuts and bolts of a large number of EU issues. In particular, their Bertelsmann Group for Policy Research will be covering the IGC as thoroughly as it covered the Convention and the previous summits. Their analyses – usually also available in English – get into the inner workings of the machinery and tell who will benefit from, for example, adapting different forms of qualified majority voting in post-enlargement Unions of 25, 27 or more. Their staff advises the German government fairly regularly, so if you want to see where the main stream of German debate on EU is flowing, this is a good place to look.
Plus, they’re outside the Brussels beltway, and indeed outside the occasionally fevered atmosphere in most national capitals. The distance tends to lend a cool, analytical slant to their writing on the EU.
If you happen to read German, their main page follows key developments on constitutional reform, defense policy and enlargement closely. The summary of the convention, Mutige Einschnitte und verzagte Kompromisse – das institutionelle Reformpaket des EU-Konvents, is a good example.
(Full disclosure: Some years back, I worked full time for the Center’s Research Group on the Global Future, and I continue to write, edit and translate for them. Take a look, and form your own opinion.)