This online textbook, provided by R. Preston McAfee (Calfornia Institute of Technology), provides a rigorous coverage of a wide range of microeconomic topics. It's a remarkably comprehensive introductory text.

An alternative introductory/intermediate textbook that focuses on optimization analysis and game theory.

An online principles text by Ted Black.

An online principles text by Robert E. Schenk.

An online economics textbook designed for a survey course in economics.

This text provides a modern treatment of macroeconomic analysis. Particular emphasis is placed on the development of the microfoundations of macroeconomic theory.

An alternative introductory/intermediate textbook with calculus that focuses on optimization analysis and game theory.

An online textbook containing a discussion of a wide variety of economics topics.

An online principles of economics textbook that makes extensive use of hypermedia.

An online version of David D. Friedman's intermediate microeconomics text.