Boron

LANL: Boron - History, sources, uses, and properties.
http://periodic.lanl.gov/elements/5.html

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

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

Visual Elements: Boron - Image, animation, source, uses, physical information, and covalent bonds.
http://www.chemsoc.org/viselements/pages/boron.html

It's Elemental: Boron - Basic physical and historical information.
http://education.jlab.org/itselemental/ele005.html

BoronWeb - Boron chemistry and links to boron chemists around the world.
http://www.chem.leeds.ac.uk/boronweb/

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

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

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

ChemGlobe: Boron - Electronic, thermal, and steric data, along with general information.
http://partisans.spurious.biz/~pkremer/projects/chemglobe/ptoe/_/5.html

Boron - Comprehensive historical data about the element and its compounds.
http://www.du.edu/~jcalvert/phys/boron.htm

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