The United States Patent and Trademark Office (USPTO) provides information on patents, trademarks and intellectual property.
Resources for Finding U.S. Patents and Patent Applications:
Resources for Information on Patent Searching:
Espacenet provides access to international patent documents and supporting patent information.
Google Patents allows you to search and read patents and patent applications from around the world.
PatentScope is provided by the World Intellectual Property Organization (WIPO) and includes access to 52 million national and international patents.