Open access e-print archive in philosophy. Formerly know as the PhilPapers Archive.
Highly respected open source encyclopedia of philosophy.
Authoritative list of sources for research on multiple Social Science and Humanities subject areas. (Ignore sign-in box on the left side of the screen.)
The main commercial reference source on philosophy.
Scholarship (articles, books, dissertations and book reviews) in philosophy.
Landmark scholarship (articles, books, dissertations and book reviews) in philosophy. Curated by a community of philosophers. Very good for exploring the study of philosophy by topic.
Full-text literature, philosophy, and theology classics online in scholarly editions, in addition to the correspondence of selected authors.