Shamelessly stolen from pretty much every MMORPG ever made, this world's vast environment and rewarding exploration justify the introduction of something that improves the speed of said exploration.
It could be basically anything... Potions with speed enhancements, NPCs in towns that grant a speed enhancing spell, possibly some other item that does it.
Just as long as it is not worn equipment - that would create a 'uniform' equipment piece, which everybody will want to have and possibly wear.
If possible, the speed buff could be suppressed for combat, in order to avoid punishing melee classes.