Over on Reddit, there is a good discussion happening on what the recipes are to create exotic gear.
As you may (or may not?) know the mystic forge allows players to throw in various items and get something back in return. Four random items will result in a random item in return, while four blue greatswords will give a blue, or sometimes a green, back. ArenaNet has stated that there is a method to the madness, and work is underway to discover that method.
One example is that Siege Weapons for WvW can be upgrade:
Upgrading Siege Weapons:
5 mithril ore + 5 elder wood log + 2 siege weapons + siege masters guide = stronger siege weapon
And here is a good explanation for some of the process behind the recipes:
Go to http://www.gw2db.com/ and then go to recipes for the craft that makes the weapon you want. Then click on one of the pearl weapons of the type you want (the affix doesn’t matter, so Berserker’s or Carrion or any of those is fine). Now look at the ingredients of that recipe. One will be an inscription, and the other two will be the components you want.
For example if you want a greatsword, you would look at http://www.gw2db.com/recipes/8487-berserkers-pearl-broadsword and see the components are Orichalcum Greatsword Blade and Orichalcum Greatsword Hilt. So then the recipe you would use is
1 scroll + 30 coins + 5 ori greatsword blade + 5 ori greatsword hilt