The following links are helpful for identifying likely sources for physical and chemical data properties.
Thermodex: an index of selected thermodynamic and physical property resources (University of Texas at Austin)
CRC Handbook of Chemistry and Physics (web edition, limited to University of Chicago users)
Contains chemical data, laboratory data, basic constants, units and conversion factors; general health and safety information; and mathematical tables.
Knovel Critical Tables (web edition, limited to University of Chicago users)
Handbook of Physical Quantities CRC Press, c1997 (Crerar 1st Floor Reference QC61 .H360 1997)
AIP Physics Desk Reference 3rd ed. Springer Verlag: New York, NY, 2003. (Crerar 1st Floor Reference QC61.A37 2003)