I've heard, by snooping around here, that there was a Pyromancer school for the Mage in DDi, and a Starlock build for the Hexblade.
Have there been any other extra builds for Essentials classes? Any domains for the Warpriest, or Virtues/Vices for the Cavalier/Blackguard?
In addition to the Pyromancer School for the Mage and Star Pact Hexblade, there was an alterate Fey Pact for the Hexblade; an Earth Domain for Warpriests; an eladrin Knight build that emphasized teleporting; staff fighting options for the knight, slayer, and thief; and an alternate class feature for cavaliers (mounts). I think that's it as far as additional builds and alternate class features for classes that appeared in HotFL and HotFK.