Not sure if this would be considered an exploit or not, feel free to move it if need be.
This could probably be used where ever there is an escort quest that doesn't have a timer attached, but I first tried it in Dustwallow last night while leveling my rogue.
What I did was first started the escort quest Thottbot World of Warcraft: Quest: Stinky's Escape, just a normal escort where you have to follow the guy and kill things that attack him.
This quest starts not to far from a cave to the west with lots of lvl 35-36 spiders that spawn very rapidly. I often grind a half a level or so there, because its fast and easy.
What you want to do is after a mob attacks the guy, start kiting it towards where you want to go, until you are attacked by another mob. Kill the first mob, and use the second mob to go further, until you get to your preferred grinding spot (the closer the better).
Once you are there, grind mobs back to back, but be sure to never actually leave combat. pull another mob before the one you are on dies.
The way the NPC is designed, he will continue to fight whatever is attacking you until combat is over, at which point he will run back to where the fight first started.
This guy in particular added a good amount of dps, and allowed me to grind out a lot faster. I would KS and bandage when health got to about 2/3, which took quite some time. There was absolutely no downtime in this grind, as the particular mobs i was fighting had very fast respawn timers. On average, it took me 17 seconds to kill one spider alone, and with him it took 12, including time I spent bandaging mid fight.
Thinking ahead, the escort in the cave in felwood may also be a good place to do this, I seem to remember her hitting rather hard.