ChemGlobe: Silicon - Electronic, thermal, and steric data along with basic information. - http://partisans.spurious.biz/~pkremer/projects/chemglobe/ptoe/_/14.html
LANL: Silicon - History, sources, uses, and properties. - http://periodic.lanl.gov/elements/14.html
Wikipedia: Silicon - Properties of the element, including its history, applications, and characteristics. - http://en.wikipedia.org/wiki/Silicon
Lenntech: Silicon - Physical data, chemical properties, and health effects. - http://www.lenntech.com/Periodic-chart-elements/Si-en.htm
EnvironmentalChemistry.com: Silicon - Atomic structure, chemical and physical properties, and table of nuclides. - http://environmentalchemistry.com/yogi/periodic/Si.html
Visual Elements: Silicon - General and physical information, source, uses, biological role, key isotopes, and ionisation energies. - http://www.chemsoc.org/viselements/pages/silicon.html
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
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/
ChemicalElements.com: Silicon - Basic information, atomic structure, and table of isotopes. - http://www.chemicalelements.com/elements/si.html
Radiochemistry of Silicon - Full text of the monograph by David R. Schink (Isotopes, a Teledyne Company, Palo Alto, California). [PDF] - http://lib-www.lanl.gov/cgi-bin/getfile?rc000059.pdf