International Patent Searching
International IP Treaties (WIPO) European Patent Database Network
espacenet.com (European Patent Office
patent searching site)
(European Patent Office patent searching site)
Delphion intellectual property network - international and US ... This is probably the finest and most sophisticated patent database website. It can do all kinds of incredible things like ranking, proximity searching, data analysis, special charting, watches and watch notices, etc. But, it is quite expensive.