ChemGlobe: Praseodymium: Electronic, thermal, and steric data along with an isotope table.
ChemicalElements.com: Praseodymium: Basic information, atomic structure, and isotopes.
EnvironmentalChemistry.com: Praseodymium: Atomic structure, chemical and physical properties, and table of nuclides.
It's Elemental: Praseodymium: Basic physical and historical information.
LANL: Praseodymium: History, uses, production, and properties.
Lenntech: Praseodymium: Physical data, chemical properties, health and environmental effects.
Praseodymium: Data tables and historic information.
Visual Elements: Praseodymium: Image, source, uses, physical information, and key isotopes.
WebElements: Praseodymium: Extensive information on history, uses, occurrence, compounds, and properties.
Wikipedia: Praseodymium: Properties of the element, including its history, applications, and characteristics.