kanad wrote to mention a ZDNet article covering the introduction of the Patent Reform Act of 2005
to the U.S. House of Representatives. From the article: "Probably the most sweeping change would be the creation of a process to challenge patents after they are granted by the Patent and Trademark Office. 'Opposition requests' can be filed up to nine months after a patent is awarded or six months after a legal notice alleging infringement is sent out. The bill is supported by the USPTO and Microsoft who have been recently asking for patent reforms ."
More details of the bill are available at the Congressman's website