A Realist View of Logic, Physics, and History: The next-to-last chapter of Popper's 1966 work Objective Knowledge. Contains a concise presentation of his epistemological views.
Against Television: An interview with Sir Karl Popper, in Italian, with an English summary.
Extracts from "The Open Society and Its Enemies": Selected passages from this 1945 work, Popper's most well-known.
From Sir Karl Popper: Selected correspondence between Thomas Szasz and Popper, between 1961 and 1984.
Language and the Body-Mind Problem: Text of this 1953 paper by Popper, with hyperlinked footnotes and a later note by the author.
Letter from Karl Popper: Scanned image of a 1992 letter to Kelley L. Ross.
Popper on Kantian Concept of War on War: Text of a 1993 interview giving Popper's take on the contemporary world situation.
Prague Lecture: Speech delivered by Popper in the Czech Republic shortly before his death.
The Problem of Induction: Text of this key 1953 paper, in which Popper presents the view of the scientific method as a critical, rather than inductive process.