Bulk Density Chart
   Densities in standard and metric form, grouped by first letter of the product.
   http://www.asiinstr.com/technical/Material_Bulk_Density_Chart_A.htm

Dielectric Constant Reference Guide
   Single page of several hundred chemicals, sorted by name, with associated dielectric constant.
   http://www.asiinstr.com/technical/Dielectric%20Constants.htm

EMSL Computational Results DataBase
   A collection of information obtained from ab initio electronic structure calculations, as well as related experimental data and literature citations. Java database interface.
   http://www.emsl.pnl.gov/proj/crdb/

EMSL Gaussian Basis Sets
   Extensible Computational Chemistry Environment Basis Set Database, Version 8/01/01, as developed and distributed by the Molecular Science Computing Facility, Environmental and Molecular Sciences Laboratory which is part of the Pacific Northwest Laboratory
   http://www.emsl.pnl.gov/forms/basisform.html

Fundamental Physical Constants from NIST
   The values of the fundamental physical constants provided at this site are recommended for international use by CODATA and are the latest available.
   http://physics.nist.gov/cuu/Constants/

GRI-Mech
   site at Berkeley also has selected kinetic rate constants and parameters for reactions involving the species included in their database.
   http://www.me.berkeley.edu/gri_mech/data/rxns_static.html

JPL Molecular Spectroscopy
   Database which has an extensive library including programs for fitting spectra and spectral line files for a large number of molecules. Use requires knowledge of spectroscopy and quantum mechanics.
   http://spec.jpl.nasa.gov/

Materials Thermochemistry (Middlesex, UK)
   Provides thermodynamic databases, data assessment, and consulting services to companies working with a variety of commercial and industrial materials. Information on training courses, models, downloads, example applications, and leasing databases.
   http://www.npl.co.uk/npl/cmmt/mtdata/

NIST Physical Reference Data
   Database holding information on fundamental physical constants, atomic spectra, molecular spectroscopic data, ionization data, X-Ray and Gamma-Ray data, radiation dosimetry data, nuclear physics data, and condensed matter physics data.
   http://physics.nist.gov/PhysRefData/contents.html

National Institute of Standards and Technology WebBook
   Thermochemical data for over 6000 organic and small inorganic compounds. Reaction thermochemistry data for over 9000 reactions. IR spectra for over 8700 compounds. Mass spectra for over 12,000 compounds. UV/Vis spectra for over 400 compounds. Electronic a
   http://webbook.nist.gov/

Naval Research Laboratory Electronic Structure Calculations Database
   Band structure, total energy, density of states, and derived quantities for most Periodic elements, hydrides, carbides, nitrides, and oxides.
   http://cst-www.nrl.navy.mil/database.html

Quantum Chemistry Literature DataBase
   A literature database on ab initio MO calculations published in major journals of Chemistry, Physics and Computer Science since 1978.
   http://qcldb2.ims.ac.jp/

Quest Consultants
   Source of thermodynamic data useful in handling phase transitions. The data are given as a function of temperature and pressure for single components and mixtures. Also links to Bubble Points, Dew Points, and Enthalpy-Pressure Diagram Pages.
   http://www.questconsult.com/~jrm/thermot.html

Surface Tension Data
   Surface tension values of some common test liquids for surface energy analysis.
   http://www.surface-tension.de

The NCI database
   
   ftp://helix.nih.gov/ncidata

The Radiation Chemistry Data Center of the Notre Dame Radiation Laboratory
   Chemical property data (such as reaction rate constants, and redox potentials,) historic bibliographic information from the RCDC bibliographic database, and recent papers in radiation chemistry and photochemistry. Also includes an on-line continuation of
   http://allen.rad.nd.edu/

University of Alberta
   Tables of chemical data for Fundamental Physical Constants, Relative Atomic Masses of the Chemical Elements, Molar Thermodynamic Properties of Pure Substances, Molar Thermodynamic Properties of Aqueous Solutes, Ionization Constants of Aqueous
   http://www.chem.ualberta.ca/courses/plambeck/p101.new/p0040x.htm