PhilPapers
philpapers.org
A comprehensive index of philosophy research with curated bibliographies, discussion forums, and categorized access to papers across all philosophical disciplines.
Why it is useful
The definitive starting point for philosophy research — the categorized bibliographies maintained by field experts are particularly valuable for understanding what the key papers are in any philosophical debate. Many entries link to freely accessible PDFs. The community annotations and reading lists are a useful supplement to formal citation searching.