The United States, as well as many other nations, provide publicly available information on patents submitted to their patent offices. In the United States, patents are regulated by the U.S. Patent and Trademark Office.
From their website, you can search through all patents and patent applications filed in the U.S. since 1790 by patent number, title, inventor, and several other keyword searches. From 1976, the records also include full-text images of the patents. Each patent also contains links to previous patents which are referenced by or which reference the patent record you are currently seeing. For example, if you do a search for Jobs, Steven limiting to inventor, you can see a patent filed by Jobs on behalf of Apple Inc. in 2006 for 'Organizing and sorting media menu items' which references dozens of other patents dating back to 1997 and is referenced by patents through 2008. This provides a useful history for anyone interested in filing a patent or understanding the development of a particular invention. You can search the U.S. Patent and Trademark Office files here: http://patft.uspto.gov/
Other nations provide various amounts of online access to their patent office files. The World Intellectual Property Organization (WIPO), an agency of the United Nations provides a pretty comprehensive list of online patent office databases by nation. You can find that list here: http://www.wipo.int/patentscope/en/dbsearch/national_databases.html
Material Safety Data Sheets (MSDS) sometimes called Product Safety Data Sheets (PSDS) are documents that detail the physical and chemical properties of specific substances. They include data deemed necessary for handling material safely including physical properties, hazards, storage, and disposal.
The US Occupational Safety and Health Administration (OSHA) requires that MSDSs be made available for potentially hazardous materials in the workplace. Data sheets are filed by CAS (Chemical Abstract Service) number although they can also be searched by chemical/material name.
Unfortunately there is no authoritative site online which organizes an provides access to MSDSs. This following commercial website provides information about where to find MSDSs and links to sites where they can be searched: http://www.ilpi.com/msds/
This is another commercial site which provides free materials data including more general information about materials, such as tensile strength: http://www.matweb.com/
Toxicity and hazardous chemical data are provided by a number of U.S. government agencies, including the National Institutes of Health (NIH), the Occupational Safety and Health Administration (OSHA), and the Environmental Protection Agency (EPA).
TOXNET is a database provided by NIH which gathers toxicity data from many government resources and provides keyword searching of the data. You can search the database by chemical name, Chemical Abstract Systems (CAS) number, or even by more general terms such as 'air pollution'. Results are grouped by the source of the data and then by the chemical name.
OSHA provides an Occupational Chemical Database with similar data as TOXNET although the database is not as extensive and the search can only be done by Chemical Name or CAS number.
The EPA's Envirofacts Master Chemical Integrator (EMCI) database provides links to toxicity data and chemical data sheets similar to the two databases mentioned. Additional EMCI also acts as a thesaurus, requiring that you search by chemical name and then listing the CAS numbers of chemicals with the searched term. If you are unsure of the CAS number of a chemical, this database will help you determine it.