Silver

Silver has the highest conductvity of the materials covered in this page.  It is also less prone to oxidation than copper but cannot match gold in this regard.  When used as plating, it can give extra zing to high frequencies because of skin effect (which dictate that high frequencies travel near the surface of a rod of conductive material).

Copper

Copper has the overall second highest conductivity of the materials commonly used in premium cables.  It is still the most commonly used conductor.  Thick runs of this can give a common HiFi sound, however any material used by itself exclusively can tend to sound a little "flat".

Gold

Electrically speaking gold falls slightly behind silver and copper in conductivity brand-new, but its performance is the most consistent because of its exemplary resistance to oxidation.  When used as plating, it can give a more mellow high frequency response (and in comparison a more powerful bass response) because of skin effect (which cause high frequencies to travel near the surface of a rod of conductive material, composed of the less conductive gold in this case)