ChemBioFinder
Free but requires registration. Search by common or trivial chemical name, chemical formula, molecular weight, or CAS registry number. Structural searches are possible using a Simplified Molecular Input Line Entry System (SMILES) in which 2- and 3-dimensional chemical structures are represented in linear textual format. Information includes chemical structure, melting, boiling and flash point, specific gravity, vapor density, water solubility, RTECS, DOT, and CAS number. (From PerkinElmer Corporation.)