Whether you're developing a new invention or would like to learn more about a currently existing one, patents serve as a useful source of information regarding existing intellectual properties, their inventors, blueprints/schematics, when they were filed, etc.
United States Patents. The full-text of patents are available free of charge. The database can be searched using any number of fields, including keyword, title, patent number, applicant name, and assignee name.
Google Patents provides access to United States patents from the 1790s to the present. It also includes patents from around the world that have been translated. Searchers can easily download the pdf of a patent found in the database.