Patents & Trademarks
A patent for an invention is a grant of property right by the Government to the inventor. In order to be issued a patent, the patentee must file specifications and a detailed description of the invention, sufficient to enable anyone skilled in the art to make use of the invention. These descriptions are later published by the government as patents.
ONLINE PATENT & TRADEMARK DATABASES
The United States Patent and Trademark Office (USPTO) maintains a searchable database of United States Patents. Full text and page images of patents issued since 1976 are available; page images of patents issued since 1790 are also included. Users can search for patents by patent number, inventor name, assignee name, classification code, and many other indexed fields. USPTO also maintains a database of patent applications filed since March 15, 2001.
In the USPTO database, full text patents are in HTML format and are readable in any Web browser; page images are in TIFF format and require a plugin that allows for viewing of TIFF image files. Click here for more information on page images of patents.
Useful links from USPTO:
General Information Concerning Patents
Glossary
How to Search
Patent and Trademark Depository Library Program (PTDLP)
The PTDLP libraries have patents, reference works, aids for searching, plus knowledgeable and experienced staff to assist with searches. A thorough search can take several hours to several days.
Search USPTO Patent Database
Cambia Patent Lens(tm) is a free full-text patent search database containing more than 8 million patents and applications worldwide.
esp@cenet searches titles and some abstracts of over 60 million patents from more than 80 countries. This is a service of the European Patent Office.
Free Patents Online is a free patent database with advance search capabilities, exportation of bibliographic information, high-quality PDF format, citation references, and XML data feeds.
Google Patent Search (Beta site), with more than 7 million U.S. patents, provides patent information (abstract, drawings, description, and claims) as well as downloadable PDF files, a link to USPTO file, and citation and reference links.
Intellectual Property Digital Library is an online Intellectual Property (IP) library providing data on patents, trademarks, industrial designs, and other IP information worldwide. This is a service of the United Nation’s World Intellectual Property Organization.
Lexis-Nexis
Academic Universe 
Patent information is under “Legal Tab” (top left). Search “Legal Searches > Patents” (on right). Users can search by type of patent (utility, design and plant) or origin ( U.S., Europe and Japan) – see “select sources” option
PATENT & TRADEMARK INFORMATION RESOURCES
Patent Search Tutorials
Patents at MIT – MIT Libraries, Massachusetts Institute of Technology. This research guide has four patent video tutorials, including a comparison of free online patent databases and searching the Free Patents Online database.
Patent Searching – McKinney Engineering Library, The University of Texas at Austin. This tutorial is guide on how to search the USPTO site.
Schreyer Business Library's Patent Search Tutorial – University Libraries, Penn State University. This tutorial provides general information on patents, searching techniques, and resources.
Research Guides
Patents Research Guide – Kelvin Smith Library, Case Western Reserve University.
Patents & Trademarks – McKinney Engineering Library, The University of Texas at Austin.
Yahoo!:Government:Law:Intellectual Property:Patents Check this subject list for other patent sites, including patents in other countries.
Yahoo!:Business and Economy:Companies:Law:Intellectual Property:Patents:Services Check this subject list for companies offering patent services.