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