WebElements: Oxygen
- Information on history, uses, occurrence, compounds, and properties of the element.
- http://www.webelements.com/webelements/elements/text/O/key.html

ChemGlobe: Oxygen
- Electronic, thermal, and steric data along with basic information.
- http://partisans.spurious.biz/~pkremer/projects/chemglobe/ptoe/_/8.html

LANL: Oxygen
- History, sources, forms, compounds, and isotopes.
- http://periodic.lanl.gov/elements/8.html

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

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

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

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

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

It's Elemental: Oxygen
- Basic physical and historical information.
- http://education.jlab.org/itselemental/ele008.html

Visual Elements: Oxygen
- Animation, uses, physical information, and key isotopes.
- http://www.chemsoc.org/viselements/pages/oxygen.html