Podcasts are a great way to review major concepts and to review for major exams.
The Federal Reserve Bank of St. Louis has an excellent podcast series called The Economic Lowdown. There are currently seven episodes available *as of April, 2011), including: Opportunity Cost, Factors of Production, The Role of Self-Interest and Competition in a Market Economy, Inflation, Unemployment, Demand, and Supply. Coming soon: Market Equilibrium.