Library and Information Science

American Association of Law Libraries
American Library Association
American Society for Information Science
American Society of Indexers
Art Libraries Society of North America
Association for Information and Image Management
Association for Information Management, Aslib
Association for Library and Information Science Education
Association of Colleges and Research Libraries. Rare Books and Manuscripts Section (USA)
Association of Independent Information Professionals
Association of Records Managers and Administrators (USA)
Association of Research Libraries
Australian Library and Information Association
Australian Society of Indexers
Canadian Library Association
Center for Research Libraries (USA)
Chinese American Librarians Association
Classification Society of North America
Commission on Preservation & Access(USA)
Institute of Information Scientists
International Association of School Librarianship, IASL
International Federation for Information and Documentation, FID Fédération Internationale d'Information et de Documentation
International Federation for Information Processing, IFIP
International Federation of Library Associations, IFLA
Library Association (UK)
Library and Information Technology Association, LITA
Medical Library Association
Research Libraries Group, RLG (USA)
Online Computer Library Center, OCLC(USA)
Schweizerischer Verband der Informatikorganisationen Fédération suisse des organisations d'informatique/Federazióne svizzera delle organizzatióni d'informatica/Swiss Federation of Information Processing Societies
Special Library Association
For library resources, try Library Information Servers, at the University of Washington, Library Resources on the Internet at the Northwestern University, NOCALL/SCALL Internet Buddies at the Northern and Southern California

You are also welcome to add on to this list by informing me of sites I have missed out.