U.S. Patent and Trademark Office
- Search Patents and Published Applications
- Index to the U.S. Patent Classification
- Classification tools
- Patents Search Templates
- Google Patent Search
- Pat2Pdf.org - patents are available in PDF format.
- Patent Lens - Search data from the World Intellectual Property Organization, European Patent Office, U.S. Patent Office, and the Australian Patent Office.
- PatentScope - search international patent applications
- FreePatentsOnline.com - offers many of the same search features as the USPTO site, but with an easier-to-use design and with the patents displayed as PDFs.
International Patent Offices:
- How to Conduct a Preliminary U.S. Patent Search: A step by step strategy - USPTO (36 minutes)
- An introduction: Why search for patents? What is a patent? MIT (5:30)