Cobalt

WebElements: Cobalt - Extensive information on history, uses, occurrence, compounds, and properties of the element.
http://www.webelements.com/webelements/elements/text/Co/key.html

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

Radiochemistry of Cobalt - Full text of the monograph by L.C. Bate (Oak Ridge National Laboratory, Oak Ridge, Tennessee). [PDF] <small>(September, 1961)</small>
http://library.lanl.gov/cgi-bin/getfile?rc000054.pdf

LANL: Cobalt - History, sources, properties, and uses.
http://periodic.lanl.gov/elements/27.html

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

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

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

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

ChemGlobe: Cobalt - Electronic, thermal, and steric data, along with isotopes table.
http://partisans.spurious.biz/~pkremer/projects/chemglobe/ptoe/_/27.html

It's Elemental: Cobalt - Basic physical and historical information.
http://education.jlab.org/itselemental/ele027.html

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