Organic Chemistry Resources Worldwide is an intuitive reference guide for synthetic organic chemists. The site is structured around the daily tasks an organic chemist has to perform.
Free chemical structure search engine. Millions of public domain structures. Very fast substructure searching. Results link to data about these structures.
ChemExper is a company joining together the areas of chemistry, computer science and telecommunication. The ChemExper Chemical Directory is a free service that allows to find a chemical by its molecular formula, IUPAC name, common name, CAS...