Google patents
Google launched a patent database that includes US patents from the 1790's through mid 2006, with plans to add patents that are more recent. Google Patents can search US and international patent classes, assignees, inventors and patent numbers. It can limit by issue and filing date. However, older scanned patents include many optical character recognition errors and the database does not include patent applications.
Taken from Online magazine, March/April 2007,pg 14.