This is a work in progress.
As far as I know, there's no compilation of info on which seal/shard drops in which quest. Here's the beginnings of such a list.
Items are listed in bold if I am certain about the information (I've seen a screenshot of that chest with the item in it, or I've pulled it myself, or I asked a guildy at the time they pulled it). Items are listed in italics if I'm taking an educated guess as to where the item drops, or if someone tells me where an item dropped but does not have a screenshot.
If you want info on a particular item (let's say you are chasing the seal of the Chainmail Coif), just search this page for 'Chainmail Coif' using your browser's search function.
If you have screenshots of a particular item's drop location, please post them.