Platinum

ChemGlobe: Platinum
Electronic, thermal, and steric data along with an isotope table.
http://partisans.spurious.biz/~pkremer/projects/chemglobe/ptoe/_/78.html

ChemicalElements.com: Platinum
Basic information, atomic structure, and isotopes.
http://www.chemicalelements.com/elements/pt.html

EnvironmentalChemistry.com: Platinum
Atomic structure, chemical and physical properties, and table of nuclides.
http://environmentalchemistry.com/yogi/periodic/Pt.html

It's Elemental: Platinum
Basic physical and historical information.
http://education.jlab.org/itselemental/ele078.html

LANL: Platinum
Sources, properties, and uses.
http://periodic.lanl.gov/elements/78.html

Lenntech: Platinum
Physical data, chemical properties, health and environmental effects.
http://www.lenntech.com/Periodic-chart-elements/Pt-en.htm

Visual Elements: Platinum
Image, general and physical information, source, uses, key isotopes, and ionisation energies.
http://www.chemsoc.org/viselements/pages/platinum.html

WebElements: Platinum
Extensive information on history, uses, occurrence, compounds, and properties.
http://www.webelements.com/webelements/elements/text/Pt/key.html

Wikipedia: Platinum
Properties of the element, including its history, applications, and characteristics.
http://en.wikipedia.org/wiki/Platinum

Radiochemistry of Platinum
Full text of the monograph by G. W. Leddicotte (Oak Ridge National Laboratory, Oak Ridge, Tennessee). [PDF] <small>(October, 1961)</small>
http://library.lanl.gov/cgi-bin/getfile?rc000037.pdf