WoW Insider have a good gallery for each instance with a list of the quests in the instance, but because they don't list how you actually get the quests (for those at the end of a chain) I'll continue with these posts, for my own benefit if no one else's. At least Drak'Tharon Keep has some quest chains to do!
- Cleansing Drak'Tharon. To get this you must first do Good Troll Hunting for Horde or Troll Season! for Alliance. These lead to Filling the Cages, completing which unlocks Truce?, the start of a quest chain which ends with Cleansing Drak'Tharon. The quest chain includes Subject to Interpretation which you need to do to unlock the other instance quest.
- Search and Rescue. This one starts with Scourgekabob, which then unlocks Seared Scourge which is the immediate prequest for Search and Rescue. However, to unlock Scourgekabob you need to complete Subject to Interpretation.
These are all level 73 and 74 quests, so it will be a while before Kam can verify the information for himself.