Cerium

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

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

ChemGlobe: Cerium - Electronic, thermal, and steric data along with a table of isotopes.
http://partisans.spurious.biz/~pkremer/projects/chemglobe/ptoe/_/58.html

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

LANL: Cerium - Sources, properties, and uses.
http://periodic.lanl.gov/elements/58.html

It's Elemental: Cerium - Basic physical and historical information.
http://education.jlab.org/itselemental/ele058.html

Visual Elements: Cerium - Image, animation, uses, general and physical information, and key isotopes.
http://www.chemsoc.org/viselements/pages/cerium.html

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

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