This search page, still in beta, focuses on a number of leading German research institutions. 

Currently this search includes the Bertelsmann Foundation, the German Council for Foreign Relations (DGAP), the Global Public Policy Institute, the Stiftung Wissenschaft und Politik (SWP), the Institut für Demoskopie/IfD-Allensbach, as well as the Centrum für Angewandte Politikforschung (CAP). Note that several economic research institutes are under the Eurozone search page. 

Further suggestions welcome.