LANL: Rubidium
Sources, properties, isotopes, and uses.
http://periodic.lanl.gov/elements/37.html

It's Elemental: Rubidium
The Element Rubidium - Basic Physical and Historical Information
http://education.jlab.org/itselemental/ele037.html

ChemicalElements.com: Rubidium
Basic information, atomic structure, and isotopes.
http://www.chemicalelements.com/elements/rb.html

Visual Elements: Rubidium
Image, source, uses, physical information, and key isotopes.
http://www.chemsoc.org/viselements/pages/rubidium.html

Lenntech: Rubidium
chemical properties, health and environmental effects of rubudium
http://www.lenntech.com/Periodic-chart-elements/Rb-en.htm

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

ChemGlobe: Rubidium
The chemical element [Rb] - Rubidium - Datasheet
http://partisans.spurious.biz/~pkremer/projects/chemglobe/ptoe/_/37.html

EnvironmentalChemistry.com: Rubidium
Comprehensive information for the element Rubidium – Rb is provided by this page including scores of properties, element names in many languages, most known nuclides and technical terms are linked to their definitions.
http://environmentalchemistry.com/yogi/periodic/Rb.html

Clocks in the Rocks
Radioactive decay processes have proven particularly useful in radioactive dating for geologic processes. Uranium-lead, potassium-argon, and rubidium-strontium dating.
http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/clkroc.html

Rubidium Ltd.
Supplies speech processing chips and solution for resource constrained consumer applications, including speech recognition, text-to-speech (TTS), biometric speaker verification, speech compression and speech detection. News and events, technology information, and downloads.
http://www.rubidium.com/