Lambda the Ultimate

To quote Richard Zach:

CSLI Lecture Notes are now part of the Stanford Medieval and Modern Thought Digitization Project. That means books such as Unger's Cut-elimination, Normalization, and the Theory of Proofs, Troelstra's Lectures on Linear Logic, Aczel's Non-well-founded Sets, van Benthem's Manual of Intensional Logic, and Goldblatt's Logics of Time and Computation are now available online and for free. (HT: Shawn)

Also of interest here will be McCarthy's Defending AI research, and Modal logic and process algebra : a bisimulation perspective, edited by Venema, de Rijke and Ponse.