General Resources in Philosophy

• The Stanford Encyclopedia of Philosophy 
• The Internet Encyclopedia of Philosophy
• The InPhO Project

Pre-Print Archives and Digital Publications

• Cognitive Sciences E-Print Archive
• Philosophers Imprint 
• PhilPapers
• PhilSci Pre-print Archive 

Historical Resources

• Perseus Digital Library
• Catalog of the Scientific Community: 16th and 17th Centuries
• Scienitific Revoluition (collection of resources and links)
• The Galilean Digital Library at the Instituto e Museo di Storia della Scienza Museum of the History of Science, Oxford
• The Huntington Library Burndy Collection in history of science and technology.
• Darwin Online
• Darwin Correspondence Project
• IsisCB (Isis Current Bibliography of history of science)