ChemSpotlight is a Spotlight metadata importer plugin for Mac OS X, which reads common chemical file formats using the Open Babel chemistry library. Spotlight can then index and search chemical data: molecular weights, formulas, SMILES, InChI, fingerprints, etc.
It’s probably easier to show the results from ChemSpotlight than to describe it. ChemSpotlight indexes chemistry files, adds molecular formulas (complete with subscripts and superscripts in the Finder), molecular weight, and a variety of other information for Spotlight searches and “Get Info” windows.
Version 2.0 is updated to include a QuickLook preview, including live freely-rotatable 3D views of your molecules and 2D views of ChemDraw and MDL molfile formats, thanks to the ChemDoodle Web Components.