Institute of Economic Theory I, Humboldt University - Research mainly on auction theory, mechanism design, industrial organization and applied game theory directed by Prof. Wolfstetter, Berlin - http://www.wiwi.hu-berlin.de/wt1/
Econometric Society - International society dedicated to advancing research in theoretical and quantitative economics. - http://www.econometricsociety.org/
Seville Game Theory Group - Lots of links on game theory, papers and publications by members and others. - http://www.esi2.us.es/~mbilbao/sevigame.htm
The ESRC Centre for Economic Learning and Social Evolution - Research on learning theory, experimental economics and evolutionary game theory at University College, London (Binmore and others) - http://else.econ.ucl.ac.uk/index.html
Center for Game Theory in Economics - Home Page of the Center for Game Theory in Economics, SUNY at Stony Brook. - http://www.sunysb.edu/gametheory/