From the ongoing era of World of Warcraft exploration, yet another significant method arises.
Specifically, the spell Blink, learned by Mages at level 20, can be used to teleport the caster partially underground using the angled surfaces of game objects. Although limited, this exploit can be used to achieve an almost infinite exploration possibility by travelling underwater, below the world's surface.
Fourteen of the possible hundred areas in which this exploit can be performed are displayed in this short movie of new, and known, exploration achievements.
Update: This exploit has apparently been nerfed as of patch 2.0.1. It is now time to argue who's fault it is.