Praxeology is the study (or logic) of human action, which is purposeful behavior. It had been popularized by Ludwig von Mises and the Austrian School of Economics.
Praxgirl's website is located here.
Episode 1, Introduction
Episode 2, Methodology
Episode 3, Purposeful Action
Episode 4, Prerequisites and Happiness
Episode 5, The Rational and Irrational
Episode 6, Ends and Means
Episode 7, Action Determines Value
Episode 8, The Concept of Time
Episode 9, Uncertainty
Additional Reading:Praxeology: The Methodology of Austrian Economics By Murray N. Rothbard
Human Action By Ludwig von Mises