For the Alliance:
Go to Shadowfang Keep, a horde instance in Silverpine Forest.
There is an undead man lying down just past the gate in the beginning of the instance.
Once you get to him, you can attack him repeatedly and he wont die.
He will loose life and collapse after a while, but you can still attack him.
My buddy used this to lvl his polearm from 10 - 200 something.
Plus many of the items that drop in SFK are exclusive to that instance, so selling them on the IF AH can net you some good cash.