This pages once listed many different articles related to Karl Popper. I can no longer do this, as it has become too unwieldy a task to maintain each link. Instead, I’ll list here only a handful of personal favorites that are on-line.
First, without question, I highly recommend Rationality versus the Theory of Rationality by William W. Bartley, III. This paper discusses the importance of moving from a context of justification to one of criticism. The implications here are vast, and I think they’ve still yet to be tapped into.
Second, there are many misconceptions regarding Karl Popper’s views of science. Ian Jarvie’s paper, Popper’s Republic of Science, demonstrates that Popper was not at all a positivists in any sense, but basically suggesting an ethical code. This is a very important paper. Eventually Jarvie expanded this paper into a book with the same name.
Third, I cannot recommend the writings of David Miller enough. His homepage contains links to several excellent on-line essays. It’s a tough choice to have to recommend only one, but I would say to start with Do We Reason When We Think We Reason, or Do We Think? [PDF] It is actually a great introduction to critical rationalism.
Fourth, Joseph Agassi is another very important thinker for those interested in critical rationalism. He also has many on-line papers. Which should you read? It’s hard to single out any paper, but I’m particular fond of Philosophy as Literature: The Case of Borges [PDF] merely because it is such a fun paper.
Fifth, I want to recommend an interview with Jeremy Sheamur, On Popper and Hayek by Richard Marshall. There’s always a lot of animated discussion over Karl Popper’s economic views. Sheamur’s remarks in this article are informative, interesting and helpful in this regards.
There are so many more great articles on-line to read, if you would like to post a favorite in the comments, please do so.