ChemGlobe: Nickel
   Electronic, thermal, and steric data along with an isotope table.
   http://partisans.spurious.biz/~pkremer/projects/chemglobe/ptoe/_/28.html

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

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

It's Elemental: Nickel
   Basic physical and historical information.
   http://education.jlab.org/itselemental/ele028.html

LANL: Nickel
   Sources, properties, and uses.
   http://periodic.lanl.gov/elements/28.html

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

Radiochemistry of Nickel
   Full text of the monograph by L. J. Kirby (Hanford Atomic Products Operation, Richland, Washington). [PDF]
   http://lib-www.lanl.gov/cgi-bin/getfile?rc000008.pdf

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

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

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