Chemistry 

CRC Atlas of Spectral Data and Physical Constants for Organic Compounds
Chemistry Reference: QD291 .C18

Dictionary of Organic Compounds

Chemical, structural, and bibliographic information on over 255,000 organic compounds

Handbook of Spectroscopy (2 vol)

Chemistry Reference: QD95 .H26 2003

NIST Chemistry Webbook

IR spectra for over 7500 compounds, Mass spectra for over 10,000 compounds, UV/Vis spectra for over 400 compounds, Electronic and vibrational spectra for over 3000 compounds

Spectral Database for Organic Compounds (SDBS)

Spectra library includes: Compound Dictionary (33,000 compounds);
MS (approx 24,000 spectra); 1H NMR (approx 14,700 spectra); 13C NMR (capprox 13,000 spectra); FT-IR (approx 51,100 spectra) ;  Raman (approx 3,500 spectra); ESR (approx 2,500 spectra);

Sigma-Aldrich Catalog

FT-NMR, FT-IR, and FT-Raman IR for many of their products