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