Silicon

Visual Elements: Silicon - General and physical information, source, uses, biological role, key isotopes, and ionisation energies.
http://www.chemsoc.org/viselements/pages/silicon.html

Lenntech: Silicon - Physical data, chemical properties, and health effects.
http://www.lenntech.com/Periodic-chart-elements/Si-en.htm

WebElements: Silicon - Extensive information on history, uses, occurrence, compounds, and properties of the element.
http://www.webelements.com/webelements/elements/text/Si/key.html

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

Silicon Chemistry Primer - Review of silicon and silicone chemistry including properties and types of materials that can be made.
http://www.dowcorning.com/content/about/aboutehs/ehssiliconchemistry.asp

ChemicalElements.com: Silicon - Basic information, atomic structure, and table of isotopes.
http://www.chemicalelements.com/elements/si.html

It's Elemental: Silicon - Basic physical and historical information.
http://education.jlab.org/itselemental/ele014.html

EnvironmentalChemistry.com: Silicon - Atomic structure, chemical and physical properties, and table of nuclides.
http://environmentalchemistry.com/yogi/periodic/Si.html

ChemGlobe: Silicon - Electronic, thermal, and steric data along with basic information.
http://partisans.spurious.biz/~pkremer/projects/chemglobe/ptoe/_/14.html

USGS Minerals Information: Silicon - Statistics and information on the worldwide supply, demand, and flow of the element (PDF format).
http://minerals.usgs.gov/minerals/pubs/commodity/silicon/

Radiochemistry of Silicon - Full text of the monograph by David R. Schink (Isotopes, a Teledyne Company, Palo Alto, California). [PDF] <small>(November, 1968)</small>
http://library.lanl.gov/cgi-bin/getfile?rc000059.pdf

LANL: Silicon - History, sources, uses, and properties.
http://periodic.lanl.gov/elements/14.html