Seeds of Destruction Tradeskill Items
Starting with Seeds of Destruction, valuable Tradeskill Items start dropping from every zone added during an expansion pack. I don't mean a new set of Cultural Items, since they can drop all over the game so long as the enemies are the right levels... I mean a few unique items specific to these expansion packs.
This expansion only adds one new item to keep your eye out for that sells very well, Chronal Resonance Dust. Despite what you may think since it's only a single item, this baby has some serious value! It's used in crafting some of the best Tradeskill Power Sources in the game. They happen to be the best Power Sources until The Darkened Sea expansion pack, at which point new ones start dropping from named enemies but are difficult to obtain.
Seeds of Destruction Pottery Guide (Sunshard Ore & Chronal Resonance Dust)
Loot these, if you don't run a trader then at the very least sell them to barters using /barter. They make some of the best droppable Power Sources for many expansions to come, currently on live servers during Ring of Scale Chronal Resonance Dust & Power Sources sell rapidly in The Bazaar.