To search patents, go to one or more of the following sites (different sites have different patents/applications/publications and different integrity issues):
Free Patents Online
This database is probably the easiest to use. The only drawback is that it is not quite as up to date as the United States Patent & Trademark Office.
United States Patent & Trademark Office – Patent Database
This is the most up-to-date database for US patents and US published patent applications.
European Patent Office
Includes European patents and published applications and some others.
Another user-friendly database to search patents.
To search trademarks registered in the US Patent and Trademark Office, go here:
United States Patent and Trademark Office – Trademarks Database
Basic is the easiest method to search, although clicking on HELP to find out more specific methods can be helpful.
Patents for sale or to be licensed can be advertised at the following website:
United States Patent and Trademark Office – Office of Data Management
Scroll down if necessary to the “Listing Patents for Sale or License in the Official Gazette (OG)”