Some institutes for organizing workshops in the sciences

Computer Sciences

Schloss Dagstuhl - Leibniz Center for Informatics (Wadern)

Mathematics

Banff International Research Station for Mathematical Innovation and Discovery (Banff)
IHES - Institut des Hautes Études Scientifiques (Paris)
Institute for Mathematics and Its Applications (Minneapolis)
Institut Mittag-Leffler (Stockholm)
International Centre for Mathematical Sciences (Edinburgh)
Mathematical Sciences Research Institute (Berkeley)
Mathematisches Forschungsinstitut Oberwolfach
Stefan Banach International Mathematical Center (Warszawa)

Physics

Aspen Center for Physics
Erwin Schrödinger Institute for Mathematical Physics (Vienna)
ECT* European Center for Theoretical Studies in Nuclear Physics and Related Areas (Trento)
Institute for Nuclear Theory (Seattle)
KITP Institute for Theoretical Physics (Santa Barbara)
International Centre for Theoretical Physics (Trieste)
Max-Planck-Institut for the Physics of Complex Systems (Dresden)
Michigan Center for Theoretical Physics (Ann Arbor)

Housing more than one discipline

CECAM - Centre Européen de Calcul Atomique et Moléculaire (Lausanne)
Institut d'Etudes Scientifiques de Cargèse (Cargèse)
Institut Henri Poincaré (Paris)
International Center for Mathematical Meetings CIRM (Mathematics, Theoretical Physics, Scientific Computing, Computer Algebra, etc...) (Marseille)
Isaac Newton Institute for Mathematical Sciences (Cambridge)
Konrad Lorenz Institute for Evolution and Cognition Research (Vienna)