ChemGlobe: Iron
   Electronic, thermal, and steric data along with an isotope table.
   http://partisans.spurious.biz/~pkremer/projects/chemglobe/ptoe/_/26.html

ChemicalElements.com: Iron
   Basic information, atomic structure, and isotopes.
   http://www.chemicalelements.com/elements/fe.html

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

It's Elemental: Iron
   Basic physical and historical information.
   http://education.jlab.org/itselemental/ele026.html

LANL: Iron
   History, sources, uses, and properties.
   http://periodic.lanl.gov/elements/26.html

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

Radiochemistry of Iron
   Full text of the monograph by J. M. Nielsen (Hanford Laboratories, Hanford Atomic Products Operation, Richland, Washington). [PDF]
   http://lib-www.lanl.gov/cgi-bin/getfile?rc000015.pdf

USGS Minerals Information: Iron
   Statistics and information on the worldwide supply, demand, and flow of the element (PDF format).
   http://minerals.usgs.gov/minerals/pubs/commodity/iron_&_steel/

Visual Elements: Iron
   Image, general and physical information, source, uses, key isotopes, and ionisation energies.
   http://www.chemsoc.org/viselements/pages/iron.html

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