Osmium

It's Elemental: Osmium - Basic physical and historical information.
http://education.jlab.org/itselemental/ele076.html

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

ChemGlobe: Osmium - Electronic, thermal, and steric data along with an isotope table.
http://partisans.spurious.biz/~pkremer/projects/chemglobe/ptoe/_/76.html

LANL: Osmium - Sources, properties, handling, and uses.
http://periodic.lanl.gov/elements/76.html

Visual Elements: Osmium - General and physical information, source, uses, key isotopes, and ionisation energies.
http://www.chemsoc.org/viselements/pages/osmium.html

ChemicalElements.com: Osmium - Basic information, atomic structure, and isotopes.
http://www.chemicalelements.com/elements/os.html

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

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

Radiochemistry of Osmium - 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?rc000023.pdf

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