(The purpose of this post is to start a thread where we can share philosophers, works and concepts which compliment or add to the common names and ideas that most of us are familiar with.)
Barry Smith - A few of his papers have been linked to on the forums before, but he’s done more than anyone I know to put the Austrian school of economics in its proper place among Austrian philosophy proper. Read this if you want to learn how Menger and the Austrian school is a special kind of Aristotelian empiricism, and whats wrong with the Kantian influence in Mises’ conception of the a priori.
Adolf Reinach - Reinach was a student of Husserl, who had a big impact on Mises. What libertarians are going to find really interesting about Reinach though, is his work "The a priori foundations of civil law." (the linked pdf is a scanned copy of an entire journal. Reinach’s paper starts about 1/4 through.) The main idea here is that certain acts logically entail legal implications – if you make a promise, you incur an obligation and create a claim which cannot be extinguished until the obligation is filled.
Chris Sciabarra - I’m pretty sure he coined the term “dialectical libertarianism.” Total Freedom is a good book if you want to learn about Hegel and dialectics from a student of Rothbard, or if you ever wondered what a dialectical treatment of Rothbardian libertarianism would look like.
Ludwig Wittgenstein - I think everyone needs to read Philosophical Investigations. Language games and the rule following paradox are pretty much essential concepts for anyone trying to figure out the world around them. Also, any Austrian seriously interested in praxeology needs to read this paper by Roderick Long.