Chemistry-related information service
(links, literature, chemistry search engines, periodic system, acronyms, units, chemistry dictionary)

National Institute of Standards and Technology
Physical constants, units and reference data. Exact values for all physical constants,
definitions of all physical units and lots of conversion factors for physical units.

Online conversion of energy equivalents (from NIST)

RCSB Protein Database (Research Collaboratory for Structural Bioinformatics)
and links to other databases of 3D macromolecular structure data

Indiana University Molecular Structure Center

Gesellschaft Deutscher Chemiker (Society of German Chemists)

Rolf Claessen's chemistry index with links to the top 5% chemistry sites, chemistry databases,
chemistry software, literature, reaction mechanisms, spectroscopy sites etc.

Two thousand of the best chemistry sites

Short introduction to the chemistry and structure of biomolecules
like amino acids, carbohydrates, lipids and nucleic acids