Well once you complete the quests in icecrown it becomes pretty clear witch ones are multibox friendly, however its pretty much everyone of them, i do 15 daily's from icecrown and the depending on the dungeon the heroic and non heroic daily's aswell, jewelcrafting daily is noce too 2 of my toons got jewelcrafting, and once you have the recipy's for jewelcrafting you need you can buy dragon's eye and they sell for about 140g-200g dependent on the server.