You can search the PubChem Molecular Database for chemical structures and molecular information directly from the Sciencebase. From this page, you can carry out a text search for entries in the rapidly growing PubChem database of small molecules from NIH. You can read David Bradley's interview with PubChem chief Steve Bryant in the Reactive Reports chemistry webzine.
To search for MSDS safety data sheets and other chemical information, please visit the ChemSpy.com search page.