Spectroscopy is the analysis of the interaction between atoms and electromagnetic radiation.
Spectroscopy is used in astronomy to determine the chemical composition of celestial bodies.
Here is a selection of some recommended sites.
ScienceofSpectroscopy.info - The Science of Spectroscopy: Wiki on spectroscopy and its theories, applications, and techniques. Considered to be one of the best wiki-based collaborations by 33 Wikis.
Please feel free to share your favorite Spectroscopy – Chemistry websites (with a short description).