United States Patent and Trademark – www.uspto.gov
The United States Patent and Trademark Office within the Department of Commerce site contains a searchable database.
United States Copyright Office within the Library of Congress – www.copyright.gov
US Copyright Office is an office of public record for copyright registration and deposit of copyright material.
European Trademark Office – http://oami.europa.eu/
The European Trademark Office site contains information about patent protection in Europe.
Google Patent Search – www.google.com/patents
Google Patent Search covers the entire collection of patents made available by the USPTO: from patents issued in the 1790’s through those issued in the middle of 2006.
Delphion Intellectual Property Network – www.delphion.com
Delphion Intellectual Property Network has searchable databases on patents and related information.