ChemGlobe: Iodine: Electronic, thermal, and steric data along with an isotope table.
ChemicalElements.com: Iodine: Basic information, atomic structure, and table of isotopes.
EnvironmentalChemistry.com: Iodine: Atomic structure, chemical and physical properties, and table of nuclides.
Iodine: Data tables and historic information.
It's Elemental: Iodine: Basic physical and historical information.
LANL: Iodine: History, sources, uses, properties, and isotopes.
Lenntech: Iodine: Physical data, chemical properties, health and environmental effects.
Radiochemistry of Iodine: Full text of the monograph by Jacob Kleinberg (University of California, Los Alamos Scientific Laboratory, Los Alamos, New Mexico and University of Kansas, Lawrence, Kansas). [PDF]
USGS Minerals Information: Iodine: Statistics and information on the worldwide supply, demand, and flow of the element (PDF format).
Visual Elements: Iodine: General and physical information, source, uses, biological role, key isotopes, and ionisation energies.
WebElements: Iodine: Extensive information on history, uses, occurrence, compounds, and properties.
Wikipedia: Iodine: Properties of the element, including its history, applications, and characteristics.