ChemGlobe: Rhenium: Electronic, thermal, and steric data along with an isotope table.
ChemicalElements.com: Rhenium: Basic information, atomic structure, and isotopes.
EnvironmentalChemistry.com: Rhenium: Atomic structure, chemical and physical properties, and table of nuclides.
It's Elemental: Rhenium: Basic physical and historical information.
LANL: Rhenium: History, sources, properties, and uses.
Lenntech: Rhenium: Physical data, chemical properties, and health effects.
Radiochemistry of Rhenium: Full text of the monograph by G. W. Leddicotte (Oak Ridge National Laboratory, Oak Ridge, Tennessee). [PDF]
Rhenium: Data tables and historic information.
USGS Minerals Information: Rhenium: Statistics and information on the worldwide supply, demand, and flow of the element (PDF format).
Visual Elements: Rhenium: General and physical information, source, uses, key isotopes, and ionisation energies.
WebElements: Rhenium: Extensive information on history, uses, occurrence, compounds, and properties.
Wikipedia: Rhenium: Properties of the element, including its history, applications, and characteristics.