Fluorine

ChemGlobe: Fluorine
Electronic, thermal, and steric data along with basic information.
http://partisans.spurious.biz/~pkremer/projects/chemglobe/ptoe/_/9.html

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

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

It's Elemental: Fluorine
Basic physical and historical information.
http://education.jlab.org/itselemental/ele009.html

LANL: Flourine
History, properties, uses, and handling.
http://periodic.lanl.gov/elements/9.html

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

Visual Elements: Fluorine
General and physical information, source, uses, key isotopes, and ionisation energies.
http://www.chemsoc.org/viselements/pages/fluorine.html

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