Hehe - I think maybe we should sticky a post entitled "Truesilver, Gold, and Silver"
These are all rare spawns of normal nodes. Silver is a rare spawn of tin and iron, Gold a rare spawn of iron and mithril, and Truesilver a rare spawn of mithril and possibly small thorium veins. What this means is that when you mine iron and mithril nodes, every once in a while one will respawn as gold or silver instead. So if you're really looking for gold, go where you would normally look for iron.
At level 30, you don't have many good options - there are a few nodes in the higher level areas of the Wetlands, and a couple in Duskwood behind the ogres, and if you're on the horde side, Thousand Needles has some (expect to die a lot if you're alliance on a PvP server). There are also a couple of reasonably safe nodes at Stonetalon mountain.
Once you get up to around level 35, the Badlands is my favorite for iron, mithril, and all the rare ores - I don't know if it's just coincidence or if the rare spawn rate differs from zone to zone, but I seem to see a lot more silver and gold in the badlands than anywhere else.
Good luck!