International

ESP@CENET is a very useful free patent search tool. Searches include United States Patents, European Patents, Japan Patents, German Patents, International (WIPO) Patents, and national patents covered in the IPANDOC database.

International Patent Applications (PCT) may be searched for at the WIPO website.

Google Patents is a useful search tool, predominantly for US patents and applications.

International IP Offices is a useful collection maintained by IP Australia.