Chlorine

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

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

Especiál Gas Inc.: Chlorine - Numeric data, uses, and general information.
http://www.c-f-c.com/specgas_products/chlorine.htm

ChemGlobe: Chlorine - Electronic, thermal, and steric data along with basic information.
http://partisans.spurious.biz/~pkremer/projects/chemglobe/ptoe/_/17.html

LANL: Chlorine - History, properties, uses, and handling.
http://periodic.lanl.gov/elements/17.html

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

It's Elemental: Chlorine - Basic physical and historical information.
http://education.jlab.org/itselemental/ele017.html

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

Visual Elements: Chlorine - Image, animation, uses, biological role, and key isotopes.
http://www.chemsoc.org/viselements/pages/chlorine.html

Chlorine Online - Information about chlorine and its derivatives from Euro Chlor.
http://www.eurochlor.org

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