Mathematics

American Mathematical Society
Australian Mathematical Society
Canadian Mathematical Society
Catalan Mathematical Society/ Societat Catalana de Matemŕtiques
Centre for Mathematics and Computer Science/ Centrum voor Wiskunde en Informatica (The Netherlands)
Chile Mathematical Society Sociedad Matemática de Chile
Danish Mathematical Society/ Dansk Matematisk Forening
Edinburgh Mathematical Society
Estonian Mathematical Society
European Mathematical Society
European Research Consortium for Informatics and Mathematics (ERCIM)
European Research Consortium for Informatics and Mathematics (France)
The Geometry Center at the University of Minnesota
German Mathematical Society/ Deutsche Mathematiker-Vereinigung
German Society for Mathematical Didactics/ Gesellschaft für Didaktik der Mathematik
Hong Kong Mathematical Society
Illinois Mathematics and Science Academy
Institute for Mathematics & its Applications
Institute of Mathematics, Jagiellonian University (Poland)
Institute of Mathematics and its Applications (UK)
International Association for Boundary Element Methods
International Association for Crytologic Research
International Federation of Nonlinear Analysts
International Linear Algebra Society
International Mathematical Union
International Society for Structural and Multidisciplinary Optimization
International Society of Dynamic Games
Israel Mathematical Union
Korean Mathematical Society
Korean Society for Industrial and Applied Mathematics
Kurt Gödel Society
London Mathematical Society
Mathematical Association of America
Mathematical Institute
Mathematics, Physics and Astronomy Society of Slovenia/ Drustvo Matematikov, Fizikov in Astronomov Slovenije
Mathematical Programming Society
Mexican Mathematical Society Sociedad Matemática Mexicana
National Council of Teachers of Mathematics, NCTM (USA)
New Zealand Mathematical Society
Singapore Mathematical Society
Société Mathématique de France
Society for Applied Mathematics and Mechanics/ Gesellschaft für Angewandte Mathematik und Mechanik (Germany)
Society for Industrial and Applied Mathematics, SIAM
Society for Mathematical Biology
Swedish Mathematical Society/ Svenska Matematikersamfundet
Turkish Mathematical Society
Unión Matématica de América Latina y del Caribe
Unione Matematica Italiana
Young Mathematicians Network

Try mathematics resources and mathematics virtual library for more info.

Statistics

American Statistical Association
Biometric Society, ENAR
The Bernoulli Society for Mathematical Statistics and Probability
The Institute for Mathematical Statistics
International Association for Statistical Computing
International Association for Statistics Education
International Society for Bayesian Analysis
Royal Statistical Society (UK)
The Statistical Society of Australia
Statistical Society of Canada/ Societe statistique du Canada
Biometrika


You are also welcome to add on to this list by informing me of sites I have missed out.
Last updated 3rd February 1998.