Hydrogen

ChemGlobe: Hydrogen - Electronic, thermal, and steric data along with basic information.
http://partisans.spurious.biz/~pkremer/projects/chemglobe/ptoe/_/1.html

Especiál Gas Inc.: Hydrogen - Numeric data, uses, and general information.
http://www.c-f-c.com/specgas_products/hydrogen.htm

Chemical of the Week: Hydrogen - Equations for reactions between hydrogen and other substances.
http://scifun.chem.wisc.edu/chemweek/HYDROGEN/hydrogen.html

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

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

It's Elemental: Hydrogen - Basic physical and historical information.
http://education.jlab.org/itselemental/ele001.html

LANL: Hydrogen - Brief reference on the element includes discussion of the sources of hydrogen, its current uses, and potential for new energy applications.
http://periodic.lanl.gov/elements/1.html

Visual Elements: Hydrogen - General and physical information, uses, and key isotopes.
http://www.chemsoc.org/viselements/pages/hydrogen.html

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

Hydrogen Energies and Spectrum - The Bohr model for an electron transition in hydrogen between quantized energy levels with different quantum numbers n yields a photon by emission with quantum energy.
http://230nsc1.phy-astr.gsu.edu/hbase/hyde.html

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