CODATA Thermodynamic Values for Key Substances http://www.codata.org/databases/key1.html
Table of internationally agreed upon values coordinated by The Committee on Data for Science and Technology. Includes the standard enthalpy of formation at 298.15 K, the entropy at 298.15 K, and the quantity H°(298.15 K)-H°(0) for elements, ions, and compounds.
Joint Expert Speciation System http://jess.murdoch.edu.au
Thermochemical database for modelling aqueous solution chemistry, including more than 230,000 critically-assessed equilibrium constants and enthalpies for about 70,000 reactions.
MELTS Supplemental Calculator http://penmelts.ess.washington.edu/MeltsCALC/
Calculator for thermodynamic data in geological systems as a function of temperature, pressure, and composition. User can select a mineral solid solution and provide either mole fractions or oxide weight percentages, and specify desired temperature and pressure.
NIST Chemistry WebBook http://webbook.nist.gov/chemistry/
This National Institute of Standards and Technology website provides thermochemical, thermophysical, and ion energetics data. Information and data on gas-phase ion, organic, and organometallic thermochemistry, as well as thermophysical properties of selected fluid systems.
WebElements Periodic Table of the Elements http://www.webelements.com/
Interactive periodic table. Clicking on an element brings up a list of general properties and data, and information on its discovery, history, uses, geologic occurrence and abundance, compounds, and chemical isolation.
