The ASD contains data for atom and ion transitions, and energy levels. Lines are included for the first 99 elements in the periodic table. ASD contains data on about 950 spectra.

Most extensive physical property/spectra site on the free web. This site provides thermochemical, thermophysical, and ion energetics data on primarily organic compounds. Compiled by National Institute of Standards and Technology.

SDBS is an integrated spectral database system for organic compounds,which includes 6 different types of spectra under a directory of the compounds.