MassBank is a mass spectral database of experimentally acquired high resolution MS spectra of metabolites. It offers various query methods for standard spectra. The database has very detailed MS data and excellent spectral/structure searching utilities.
NIST Atomic Spectra Database
The Atomic Spectra Database (ASD) contains data for radiative transitions and energy levels in atoms and atomic ions. Data is included for observed transitions of 99 elements and energy levels of 56 elements.
NIST Chemistry WebBook
IR spectra for over 7,500 compounds, Mass spectra for over 10,000 compounds, UV/Vis spectra for over 400 compounds, Electronic and vibrational spectra for over 3000 compounds.
UV/Vis Spectra Data Base
Spectral information (gas, liquid and solid phase from EUV-VUV-UV-Vis-NIR) and related data from published papers. The free database currently contains about 5,700 and data sheets (metadata) for about 900 substances.