Tom Palley provides a very clear and insightful description of the post-Keynesian school of economics by tracing back its connections to the different historical schools of thought.
One of the most authoritative authors on the intellectual heritage of John Maynard Keynes, Robert Skidelsky draws a sketch of the great man's economic thinking both accessible and insightful.
Anwar Shaikh seeks in his lectures for alternative explanations for empirically observed macro and microeconomic patterns of economic fluctuations, price volatility, and economic development.