ChemGlobe: Mercury - Electronic, thermal, and steric data along with an isotope table.
ChemicalElements.com: Mercury - Basic information, atomic structure, and isotopes.
EnvironmentalChemistry.com: Mercury : Nuclides - Extensive information on the nuclides of mercury, including potential parent nuclides.
It's Elemental: Mercury - Basic physical and historical information.
LANL: Mercury - Basic information, history, and uses.
Lenntech: Mercury - Physical data, chemical properties, health and environmental effects.
Mercury - A very brief description of Mercury, with a good diagram of its electron orbitals.
Mercury and Methylmercury by IC-ICPMS - Analysis of biological, pharmaceutical, and environmental samples for methylmercury and mercury.
Mercury in Space - Answers the question of what happens to Mercury in space.
Mercury in the Laboratory - Practical considerations when working with mercury in the laboratory.
USGS Minerals Information: Mercury - Statistics and information on the worldwide supply, demand, and flow of the element (PDF format).
Vermont Legislative Research Shop - Mercury Information - Features basic information about Mercury, as well as its harmful effects and legislation concerning Mercury in some American States.
Visual Elements: Mercury - Image, general and physical information, source, uses, key isotopes, and ionisation energies.
WebElements: Mercury - Contains extensive information about Mercury, as well as pictures and videos that show its physical appearance and how it reacts with certain chemicals.
Why is Mercury liquid at room temperature? - Explores the question of why Mercury is liquid at room temperature. It also provides some links to other sites regarding this chemistry quandary.
Wikipedia: Mercury - Properties of the element, including its history, applications, and characteristics.
Radiochemistry of Mercury - Full text of the monograph by Josef Roesmer (Westinghouse Astronuclear Laboratory, Pittsburgh, Pennsylvania). [PDF] (September, 1970)