Stanford Encyclopedia of Philosophy
Organises scholars from around the world in philosophy and related disciplines to create and maintain an up-to-date reference work.
Internet Encyclopedia of Philosophy
Provides open access to detailed, scholarly information on key topics and philosophers in all areas of philosophy.
Oxford University Press's Very Short Introductions offer introductions to a diverse range of subject areas. All titles provide introductions to a range of subjects, combining facts, analysis, new ideas to make the topics readable.