Google Patent Search

Google has launched Google Patent Search, a web
search engine that allows researchers to retrieve the
entire collection of patents made available by the
USPTO from the 1790s through those issued through
mid-2006. The site does not currently include patent
applications, international patents, or U.S. patents issued
over the last few months, but Google hopes to expand
coverage in the future.

Patent Search works like Google Book Search. Google has
converted the entire image database of U.S. patents into a
searchable format. You can search the full text of U.S. patents
from the Google Patent Search homepage, or visit the
Advanced Patent Search page to search by criteria like
patent number, inventor, and filing date.