U.S. Patent and Trademark Office – The USPTO web site includes links to searchable databases of issued patents, published patent applications, pending and registered trademarks, a roster of registered patent attorneys and patent agents, and other information of interest.

Delphion Web Site – The Delphion Intellectual Property Network (IPN) provides access to a wide variety of patent data collections and related information.  Searching, browsing, and viewing of patents is fee-based.

European Patent Office – The European Patent Office provides searchable databases that include European Patents, World Intellectual Property Organization Patents, and Japanese Patents.

Google Advanced Patent Search – Google Advanced Patent Search enables searching of patents based upon keywords and other parameters and enables patent drawings to be displayed in the browser window without using a plug-in.