Moonglade -> Argent Vanguard (Icecrown)
First off this involves you not continuing a quest change, so bad luck to the people who have already completed this.
There is a quest in Icecrown (Starting with A Tale of Valor) that involves you travelling to moonglade and entering the emerald dream, after completing this quest you get a portal to Icecrown upon accepting The Boon of Remulos.
Here's the "exploit". If you abandon the quest and accept it again, he will make another portal to Icecrown. Meaning if your hearth is down, you can simply teleport to moonglade, go to Remulos and accept this quest, go to Icecrown and abandon it again.
This may also be useful if you're not a druid, say you're near moonglade and your hearth is down and not near an instance.
The quest chain does eventually end up with some nice Blues and lots of gold/exp, but personally as a druid this seems better.
Wasn't sure if this is the right section, because it is kinda exploiting the quest by abandoning and accepting it, although it could be seen as "Working as Intended".