I/P Updates notes the release of new USPTO Interim Guidelines for Examination of Patent Applications for Patent Subject Matter Eligibility, signed on Oct. 26, 2005.

And the ever-estimable Patently-O analyzes them:

The crux of the new guidelines is that an invention falls within the scope of 35 U.S.C. 101 “if the claimed invention physically transforms an article or physical object to a different state or thing, or if the claimed invention otherwise produces a useful, concrete, and tangible result.” The application itself should enable one of ordinary skill in the art to understand the utility of the invention.