US Patent and Trademark Office USPTO. 
The USPTO site allows you to search US patent databases for patents back to 1974 as well as World intellectual Property Organization (WIPO), European Patents and Applications, and Japanese patent information.

LexisNexis Academic.  Go to Legal Research.... Patents and  search all U.S. patents from 1971 to present or the manual of classification. Also, use this to search for news and articles in newspapers, magazines and journals.

International Patent Offices. Search by country.

Also see Patent Research  for a more complete guide.