ChemGlobe: Tin: Electronic, thermal, and steric data along with an isotope table.
ChemicalElements.com: Tin: Basic information, atomic structure, and isotopes table.
EnvironmentalChemistry.com: Tin: Atomic structure, chemical and physical properties, and table of nuclides.
It's Elemental: Tin: Basic physical and historical information.
LANL: Tin: Sources, properties, forms, and handling.
Lenntech: Tin: Physical data, chemical properties, health and environmental effects.
Radiochemistry of Tin: Full text of the monograph by W. E. Nervik (Lawrence Radiation Laboratory, University of California, Livermore, California). [PDF]
Tin: Data tables and historic information.
USGS Minerals Information: Tin: Statistics and information on the worldwide supply, demand, and flow of the element (PDF format).
Visual Elements: Tin: Image, general and physical information, source, uses, key isotopes, and ionisation energies.
WebElements: Tin: Extensive information on history, uses, occurrence, compounds, and properties.
Wikipedia: Tin: Properties of the element, including its history, applications, and characteristics.