Phosphorus

ChemGlobe: Phosphorus
Electronic, thermal, and steric data along with basic information.
http://partisans.spurious.biz/~pkremer/projects/chemglobe/ptoe/_/15.html

ChemicalElements.com: Phosphorus
Basic information, atomic structure, and table of isotopes.
http://www.chemicalelements.com/elements/p.html

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

It's Elemental: Phosphorus
Basic physical and historical information.
http://education.jlab.org/itselemental/ele015.html

LANL: Phosphorus
Properties, handling, production, and uses.
http://periodic.lanl.gov/elements/15.html

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

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

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

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

Radiochemistry of Phosphorus
Full text of the monograph by William T. Mullins and G. W. Leddicote (Oak Ridge National Laboratory, Oak Ridge, Tennessee). [PDF] <small>(March, 1962)</small>
http://library.lanl.gov/cgi-bin/getfile?rc000024.pdf