I have a good supply of gold; however I do not know what to do with it all! Golden armour and tools wear out too fast to be useful, so what do I do with all my gold?
I'm not really a Minecraft player, but a quick glance at the wiki indicates that you should (like with other metals) first smelt raw gold ore in to Gold Ingots, using a furnace.
You can also combine 9 ingots in to a Gold Block, these can then be used for construction (if you want a nice golden house or something) or these ingots can then be used to craft a Golden Apple, which instantly restores your health.
Given the supposed rare nature of Gold within the game and the items you can create with it, I would presume Gold's most important usage is in the creation of Powered Rail, which (from what I see here) vastly increases your construction options with mine carts.
With the new villager trading feature that was added in version 1.3 you can now buy and sell items using emeralds as currency. All of the 5 villager types have a chance that they may offer to buy gold from you, but a Blacksmith is more likely to offer this trading option.
So, if you don't use your gold for much else, I'd say hold on to it until you find a villager who will buy it from you. It's a good way to amass emeralds.
This article contains a list of all of the uses of gold, however in general gold is only used for Clocks, powered rails, and as a fancy looking block. It can be used to craft armor and tools as well, but they have such low durability you should never use it for that purpose. It also needs to be mentioned that gold is a somewhat rare resource, so you don't want to waste it.
Overall, the most useful application is powered rails. This is because powered rails are essential for making minecart tracks, and you'll often need quite a few of them. Clocks on the other hand are only used to tell the time, which can be helpful, but is far from required. However you only need to make one clock, so most people will spend the gold to make one. Finally they can be used as blocks as well, although it's more practical to use something else. However if you have a lot of extra gold lying around, it can be a nice way of making your base look nice and fancy.
Another interesting feature of gold is that it has much higher enchantability than any other material in the game; meaning that when you use gold items, you are more likely to get a more powerful enchantment. For many things, this just isn't interesting, Gold armor with the protection enchantment is not better than plain iron armor; but there's no real downside to having a diving helmet that happens to be made of gold; so for many of those sorts of speciality bonuses, Gold items are still quite good.