How can I find the location of a given item by looking at the world data?

Is there a way to search through world data to find instances of a given type of item (e.g., gold horse armor) and/or to find an item with a particular name?

My goal is to find the item's location within the in-game world, ideally with an X/Y/Z coordinate. My specific application is locating stolen items, but I can imagine other uses for such a search, for example, locating mob spawners.

Hopefully there's already a utility or technique available to help with this. But if not, some documentation on the structure of world data might do the trick, as I'm a programmer and could probably write the search myself.

MCEdit is what you are looking for if you want to remove blocks. I don't think it does items, but something like InvCheck can let you browse inventories of players. Items mobs are holding is another thing entirely, and I don't know of anything that does that.