ChemGlobe: Caesium
- Electronic, thermal, and steric data along with an isotope table.
- http://partisans.spurious.biz/~pkremer/projects/chemglobe/ptoe/_/55.html

LANL: Cesium
- History, sources, properties, and costs.
- http://periodic.lanl.gov/elements/55.html

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

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

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

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

It's Elemental: Cesium
- Basic physical and historical information.
- http://education.jlab.org/itselemental/ele055.html

ChemicalElements.com: Cesium
- Basic information, atomic structure, and isotopes table.
- http://www.chemicalelements.com/elements/cs.html

Radiochemistry of Cesium
- Full text of the monograph by M. T. Kinsley (Brookhaven National Laboratory, Upton, New York). [PDF]
- http://lib-www.lanl.gov/cgi-bin/getfile?rc000032.pdf

Visual Elements: Caesium
- Image, general and physical information, and key isotopes.
- http://www.chemsoc.org/viselements/pages/caesium.html