from HyperPhysics portal. This is rather a comprehensive online physics handbook containing "Thermodynamics" chapter. Site has a handle navigation, good illustrations, and very detail content.

Definition and short explanations of terms, units and basic principles.

from Engineers Edge. A definitions, short explanations and connection of basic thermodynamics terms.

Calculation of metal phase diagrams using the CALPHAD method. Also offers consulting services.

TEST is a visual environment to solve thermodynamics problems, pursue what-if scenarios and perform numerical experiments.

Lecture notes and problems from University of Pittsburg.

Applet illustrating the ideal gas law : action of a piston in a pressure chamber filled with ideal gas.

The basis for thermodynamics. An introduction to the conservation of energy, states of matter and changes of state.

Online book on Thermodynamics at UC Berkeley.

A qualitative introduction to the second law and entropy written for beginners in chemistry but useful for physics students too. Explains relationship with Murphy's Law.