Magnesium

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

ChemicalElements.com: Magnesium - Basic information, atomic structure, and table of isotopes.
http://www.chemicalelements.com/elements/mg.html

ChemGlobe: Magnesium - Electronic, thermal, and steric data along with basic information.
http://partisans.spurious.biz/~pkremer/projects/chemglobe/ptoe/_/12.html

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

LANL: Magnesium - History, properties, uses, compounds, and handling.
http://periodic.lanl.gov/elements/12.html

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

Radiochemistry of Magnesium - Full text of the monograph by A. W. Fairhall (Dept. of Chemistry, University of Washington, Seattle, Washington). [PDF] <small>(January, 1961)</small>
http://library.lanl.gov/cgi-bin/getfile?rc000047.pdf

WebElements: Magnesium - Extensive information on history, uses, occurrence, compounds, and properties of the element.
http://www.webelements.com/magnesium/

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

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

It's Elemental: Magnesium - Basic physical and historical information.
http://education.jlab.org/itselemental/ele012.html