ChemGlobe: Ruthenium: Electronic, thermal, and steric data along with an isotope table.
ChemicalElements.com: Ruthenium: Basic information, atomic structure, and table of isotopes.
EnvironmentalChemistry.com: Ruthenium: Atomic structure, chemical and physical properties, and table of nuclides.
It's Elemental: Ruthenium: Basic physical and historical information.
LANL: Ruthenium: History, sources, uses, and properties.
Lenntech: Ruthenium: Physical data, chemical properties, and health effects.
Ruthenium: Data tables and historic information.
Visual Elements: Ruthenium: Image, discovery, uses, source, and physical information.
WebElements: Ruthenium: Extensive information on history, uses, occurrence, compounds, and properties.
Wikipedia: Ruthenium: Properties of the element, including its history, applications, and characteristics.