Nice site: FreePatentsOnline
FreePatentsOnline search engine is one of the most powerful, fastest and easiest patent search engines on the web.
The search allows advanced search techniques such as word stemming, proximity searching, relevancy ranking and search term weighting to help you find exactly what you are looking for.
And, personal account features let you organize, annotate and share documents, and Alerts let you instantly be notified when new documents of interest are published.
My advise: don’t use the the basic form on the homepage (because it searches only on US patents), go directly on advanced search.