HSDB (Hazardous Substances Data Bank) is a database of peer reviewed data on 5,000 potentially hazardous substances and forms part of the TOXNET cluster of databases provided free by the National Library of Medicine.  Fully referenced detailed quantitative data are given for each compound including toxicological, chemical and physical properties.  Each entry also includes information on 

• uses
• human health effects
• emergency handling procedures
• disposal methods

The database is browsable and searchable by compound name or CAS Registry Number. Records can be fully or partially downloaded.  

Check out the free of charge chemical information link for other useful resources