Dictionary of Sorts: Philosophical terms mostly from ethics and epistemology, edited by Robert Berman.
ISCID Encyclopedia of Science and Philosophy: A free, community developed resource containing information on both science and philosophy.
Larry Hauser's Mostly Modern Philosophical Glossary: Glossary of philosophical terms focusing on modern philosophy.
Meta-Encyclopedia of Philosophy: A list of philosophical terms and names linked to the major encyclopedias and dictionaries of philosophy on the internet.
PhiloSophos: Includes philosophy papers, university distance learning programs and college correspondence courses, and a philosophy dictionary.
Philosophy Dictionaries and Encyclopedias: Collection of links to philosophy reference sources.
Routledge Encyclopedia of Philosophy: Online edition. Free access to sample contents, full access by subscription.
The Ism Book: A dictionary of philosophies from Peter Saint-André, editor of the Monadnock Review.
Think: Philosophy: Philosophy resource for beginners. Contains philosophers, schools of thought, and topics.
Wikipedia: Philosophy: The entrance page to all articles in the philosophy section of the free encyclopedia.