Helium

ChemicalElements.com: Helium - Basic information, atomic structure, and table of isotopes.
http://www.chemicalelements.com/elements/he.html

LANL: Helium - History, sources, properties, and uses.
http://periodic.lanl.gov/elements/2.html

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

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

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

ChemGlobe: Helium - Electronic, thermal, and steric data along with basic information.
http://partisans.spurious.biz/~pkremer/projects/chemglobe/ptoe/_/2.html

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

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

Visual Elements: Helium - Image, animation, discovery, uses, physical information, and key isotopes.
http://www.chemsoc.org/viselements/pages/helium.html

It's Elemental: Helium - Basic physical and historical information.
http://education.jlab.org/itselemental/ele002.html

Corrosionsource.com: Helium - History, sources, properties, isotopes, and uses.
http://www.corrosionsource.com/handbook/periodic/2.htm

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