(This is my original Spigot version of Thoroughfabric)
This plugin adds "desire paths" to your world -- as you trace the same paths over and over, the blocks will slowly change beneath your feet.
First from grass/dirt/podzol/mycelium to coarse dirt. Then from coarse dirt to path blocks. You can also elect to let the path blocks wear away into cobblestone slabs.
Riding mobs can have more of an effect as well: horses and camels have rather heavy steps that will wear paths faster (only when ridden by a player, though).
Maybe you're using this to plan infrastructure; maybe you want the extra mechanic of having to maintain your paths; or maybe you just want to give your world that "lived-in" look.
Happy trails!
