Links to categories on the internet:

• Theory and Applications of Categories  -  Electronic jounrnal on category theory.
• Category Theory Mailing List 
• Hypatia directory of research workers in Computer Science and Pure Mathematics, and a library of their papers.
• Stanford Encyclopedia of Philosophy
• Abstract and Concrete Categories - The Joy of Cats (J. Ad�mek, H. Herrlich, G. E. Strecker): Download PDF-File
• TheCasters - Videos on various topics in category theory.