ChemicalElements.com: Osmium
Basic information, atomic structure, and isotopes.
EnvironmentalChemistry.com: Osmium
Atomic structure, chemical and physical properties, and table of nuclides.
It's Elemental: Osmium
Basic physical and historical information.
Lenntech: Osmium
Physical data, chemical properties, health and environmental effects.
Radiochemistry of Osmium
Full text of the monograph by G. W. Leddicotte (Oak Ridge National Laboratory, Oak Ridge, Tennessee). [PDF]
Visual Elements: Osmium
General and physical information, source, uses, key isotopes, and ionisation energies.
WebElements: Osmium
Extensive information on history, uses, occurrence, compounds, and properties.
Wikipedia: Osmium
Properties of the element, including its history, applications, and characteristics.