A collection of online and offline spectral libraries for the diy spectrometer project:
I believe most of these are either for remote sensing or for astronomy, so sample-based spectral libraries may be different:
- http://vpl.astro.washington.edu/spectra/allmoleculeslist.htm
- HITRAN data for specific molecules: http://archive.publiclaboratory.org/hitran-spectral-library/
- ASTER library for remote sensing/hyperspectral data, mostly land types: http://archive.publiclaboratory.org/aster-spectral-library/