Britannica Nobel Prize: Helium: Detailed overview and data.
ChemGlobe: Helium: Electronic, thermal, and steric data along with basic information.
ChemicalElements.com: Helium: Basic information, atomic structure, and table of isotopes.
Corrosionsource.com: Helium: History, sources, properties, isotopes, and uses.
EnvironmentalChemistry.com: Helium: Atomic structure, chemical and physical properties, and table of nuclides.
Especiál Gas Inc.: Helium: Numeric data, uses, and general information.
Helium: Data tables and historic information.
It's Elemental: Helium: Basic physical and historical information.
LANL: Helium: History, sources, properties, and uses.
Lenntech: Helium: Physical data, chemical properties, and health effects.
USGS Minerals Information: Helium: Statistics and information on the worldwide supply, demand, and flow of the element (PDF format).
Visual Elements: Helium: Image, animation, discovery, uses, physical information, and key isotopes.
WebElements: Helium: Extensive information on history, uses, occurrence, and properties of the element.
Wikipedia: Helium: Properties of the element, including its history, applications, and characteristics.