Professional Associations:The following is an Index of interesting philosophy pages which although not exhaustive, I find helpful.
Professional Associations:
American Philosophical Association
American Association of Philosophy Teachers
The Hume Society
The Society of Christian Philosophers
The Kurt Godel Society
The American Nihilism Association
American Society for Aesthetics
Resources:Philosophy - Virtual Library - in the UK (a bit slow)
Philosophy on the Web - a nice collection of useful links
Ejournals
Graduate Departments
The Center for Dewey Studies
The Voltaire Foundation
The Noam Chomsky Archive
Philosopher Pages:The Nietzsche Page
The Charles S. Peirce Page
The Plato Page
The Aristotle Page
The Descartes Page
The Hobbes Page
The Locke Page
The Hume Page
The Wittgenstein Page
Resources in Political Philosophy:Political Philosophy Main Page - a nice Oxford site (but very slow!)
Classical Period (Socrates, Plato, Aristotle, Augustine)
Modern Period (Machiavelli to Locke)
Modern Period (Burke to Marx)
Contemporary Resouces in Political Theory
Universal Philosophy Index:Bjorn's Guide to Philosophy (An Excellent, Substantive, Resource)
Sean's One-Stop Philosophy Shop (you can find just about any link here)A Philosophy Resources Page (by John Stemmer)
Philosophy on the Internet (by Dey Alexander)