This is it! Funcom, in partnership with Eidos and IGN have announced the Age of Conan open beta, available at FilePlanet.com and other IGN partner sites. Now, being available on FilePlanet means it's more of an 'exclusively open beta' -- you will have to be a member to receive the download.
Additionally, from the press release: 'Funcom would like to point out that the primary function of the Open Beta is to stress test Age of Conan prior to launch. This means that Funcom will not make the entire game available to the Open Beta testers, and a level 13 cap will be applied.' So no matter how quickly you progress through the content, you're not going to be able to see any of the higher-level stuff; this might mean no siege warfare, or city building, or ridable mounts. But you've waited this long for decapitation-related joy, and here it is!