Cadmium: Data tables and historic information.
ChemGlobe: Cadmium: Electronic, thermal, and steric data along with an isotope table.
ChemicalElements.com: Cadmium: Basic information, atomic structure, and isotopes.
EnvironmentalChemistry.com: Cadmium: Atomic structure, chemical and physical properties, and table of nuclides.
It's Elemental: Cadmium: Basic physical and historical information.
LANL: Cadmium: Basic information, history, uses, and cost.
Lenntech: Cadmium: Physical data, chemical properties, health and environmental effects.
USGS Minerals Information: Cadmium: Statistics and information on the worldwide supply, demand, and flow of the element (PDF format).
Visual Elements: Cadmium: Image, uses, physical information, key isotopes, and ionisation energies.
WebElements: Cadmium: Extensive information on history, uses, occurrence, compounds, and properties.
Wikipedia: Cadmium: Properties of the element, including its history, applications, and characteristics.