Niobium
Links
Visual Elements: Niobium
http://www.chemsoc.org/viselements/pages/niobium.html
Image, uses, general information, and ionisation energies.
It's Elemental: Niobium
http://education.jlab.org/itselemental/ele041.html
Basic physical and historical information.
ChemicalElements.com: Niobium
http://www.chemicalelements.com/elements/nb.html
Basic information, atomic structure, and isotopes.
USGS Minerals Information: Niobium
http://minerals.usgs.gov/minerals/pubs/commodity/niobium/
Statistics and information on the worldwide supply, demand, and flow of the element (PDF format).
EnvironmentalChemistry.com: Niobium
http://environmentalchemistry.com/yogi/periodic/Nb.html
Atomic structure, chemical and physical properties, and table of nuclides.
WebElements: Niobium
http://www.webelements.com/webelements/elements/text/Nb/key.html
Extensive information on history, uses, occurrence, compounds, and properties of the element.
Wikipedia: Niobium
http://www.wikipedia.org/wiki/Niobium
Properties of the element, including its history, applications, and charateristics.
Lenntech: Niobium
http://www.lenntech.com/Periodic-chart-elements/Nb-en.htm
Physical data, chemical properties, and health effects.