Britannica Nobel Prize: Technetium: Overview and basic data.
ChemGlobe: Technetium: Electronic, thermal, and steric data along with an isotope table.
ChemicalElements.com: Technetium: Basic information, atomic structure, and isotopes.
EnvironmentalChemistry.com: Technetium: Atomic structure, chemical and physical properties, and table of nuclides.
It's Elemental: Technetium: Basic physical and historical information.
LANL: Technetium: History, isotopes, properties, and handling.
Lenntech: Technetium: Physical data, chemical properties, and health effects.
Radiochemistry of Technetium: Full text of the monograph by Edward Anders (Enrico Fermi Institute and Dept. of Chemistry, University of Chicago, Chicago, Illinois). [PDF format]
Technetium: Data tables and historic information.
Visual Elements: Technetium: Image, general and physical information, source, uses, key isotopes, and ionisation energies.
WebElements: Technetium: Extensive information on history, uses, occurrence, compounds, and properties.
Wikipedia: Technetium: Properties of the element, including its history, applications, and characteristics.