Via TM Travel World, Marriott is offering free Gold status for 90 days.
The offer states valid through February 28, 2011, so you may want to wait until you have Marriott stays planned. On the other hand, Marriott could pull the offer at any time so you might want to play it safe and grab the status now. They do want an Air China PhoenixMiles number on the signup page, though, so you at least need to enter one. The offer includes bonus Air China miles for Marriott stays.
The offer is valid for existing and for new members, and is being marketing to Air China PhoenixMiles members but membership in the Air China program isn’t required (not that it would be hard to join if it were!).