Tungsten

ChemicalElements.com: Tungsten - Basic information, atomic structure, and isotopes.
http://www.chemicalelements.com/elements/w.html

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

LANL: Tungsten - Basic information and history.
http://periodic.lanl.gov/elements/74.html

WebElements: Tungsten - Extensive information on history, uses, occurrence, compounds, and properties.
http://www.webelements.com/webelements/elements/text/W/key.html

It's Elemental: Tungsten - Basic physical and historical information.
http://education.jlab.org/itselemental/ele074.html

ChinaTungsten Online - Basic properties, compounds, brief history, information about production processes.
http://chinatungsten.com/chwurl-2-1.htm

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

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

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

Radiochemistry of Tungsten - Full text of the monograph by G. W. Leddicotte (Oak Ridge National Laboratory, Oak Ridge, Tennessee). [PDF] <small>(September, 1961)</small>
http://library.lanl.gov/cgi-bin/getfile?rc000011.pdf

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

ChemGlobe: Tungsten - Electronic, thermal, and steric data along with an isotope table.
http://partisans.spurious.biz/~pkremer/projects/chemglobe/ptoe/_/74.html