An the subject of search engines for DWF and DWG files there is cadbot.com. Unlike DocuPoint Discovery, cadbot.com is not intended for internal sites and instead just allows you to search for CAD files available on the public Internet. Whilst it is not as useful as searching your own resources it is still nice to keep in mind if looking for a CAD model of some description.
David Harrison's musings on collaboration and I.T.