HardOCP has a report and photos of a Sapphire Radeon X850XT cooling system that apparently utilizes a form of liquid metal cooling. What appears to be stainless steel tubing is connected to a kinetic pump, and GPU block and heat exchanger. According to the report which is coming from the floor of Computex 2005, the working fluid in Sapphire's cooling system is the element Gallium.
Accordingly; "Gallium is the only metal, except for mercury, caesium, and rubidium, which can be liquid near room temperatures; this makes possible its use in high-temperature thermometers. It has one of the longest liquid ranges of any metal and has a low vapour pressure even at high temperatures."