British Library - Patents
Features extensive information on patents, trademarks and intellectual property. Provides useful well maintained list of links including tutorials, patent databases, patent attorneys, translation services, legislation, litigation and statistical analysis.

Espacenet
Free worldwide database of patent records provided by the European Patent Office. It offers information, searchable by keyword, bibliographic and classification details, about published patent applications from over 70 different countries and regions. Full-text is available in most cases, backfile coverage depends on the country of the patenting authority, some of the oldest facsimiles date back to 1888. Documents are linked where available to the patent family and legal status information. Thorough definitions for these and other patenting/intellectual property terms are available on the website.

Free Patents Online
A free patents database containing all patents published by the United States Patent and Trademark Office (USPTO) and partial European data from 1976 to present. Updated weekly, with free PDF downloading, free account features including RSS feeds and a powerful search engine searchable by keyword and bibliographic detail.

Japanese Patent Office
Free access to the searchable Industrial Property Digital Library (IPDL).

Patents Endorsed Licence of Right (LOR) and Patents Not in Force (NIF) databases
Two databases from the United Kingdom Intellectual Property Office which will help businesses identify opportunities they might otherwise not have found.

UK Intellectual Property Office
Provides useful information on patents including the definition of a patent, benefits of patent protection, a brief history, how to apply for patents, essential technical, legal and other background information and contact points.

USPTO
Full text of US patents (from 1976) and full page images (from 1790), available free from the United States Patent and Trademark Office.