Helium
Links
Britannica Nobel Prize: Helium
http://www.britannica.com/nobel/micro/713_23.html
Detailed overview and data.
ChemicalElements.com: Helium
http://www.chemicalelements.com/elements/he.html
Basic information, atomic structure, and table of isotopes.
Corrosionsource.com: Helium
http://www.corrosionsource.com/handbook/periodic/2.htm
History, sources, properties, isotopes, and uses.
EnvironmentalChemistry.com: Helium
http://environmentalchemistry.com/yogi/periodic/He.html
Atomic structure, chemical and physical properties, and table of nuclides.
Especil Gas Inc.: Helium
http://www.c-f-c.com/specgas_products/helium.htm
Numeric data, uses, and general information.
It's Elemental: Helium
http://education.jlab.org/itselemental/ele002.html
Basic physical and historical information.
Lenntech: Helium
http://www.lenntech.com/Periodic-chart-elements/He-en.htm
Physical data, chemical properties, and health effects.
USGS Minerals Information: Helium
http://minerals.usgs.gov/minerals/pubs/commodity/helium/
Statistics and information on the worldwide supply, demand, and flow of the element (PDF format).
Visual Elements: Helium
http://www.chemsoc.org/viselements/pages/helium.html
Image, animation, discovery, uses, physical information, and key isotopes.