[W]e wanted to make it easier for people to understand the world of inventions, whether they were browsing curious patents or researching serious engineering.That's why we're proud to announce that the USPTO and Google are making this data available for free at http://www.google.com/googlebooks/uspto.html. This includes all granted patents and trademarks, and published applications - with both full text and images. In the future we will be making more data available including file histories and related data.
Google Patents is in beta version, includes over 7 million patents, and includes advanced search option. You can read more about Google patents here.