Google Patent Search
http://www.google.com/patents/

With Google Patent Search, you can now search the full text of the U.S. patent corpus and find patents that interest you. All patents available through Google Patent Search come from the United States Patent and Trademark Office (USPTO). Patents issued in the United States are public domain government information, and images of the entire database of U.S. patents are readily available online via the USPTO website. Google Patent Search covers the entire collection of patents made available by the USPTO—from patents issued in the 1790s through those issued in the middle of 2006. They don’t currently include patent applications, international patents, or U.S. patents issued over the last few months, but they look forward to expanding their coverage in the future. To date, the USPTO has issued approximately 7 million patents. This has been added to the tools section of Research Resources Subject Tracer™ Information Blog.