Square Enix MMO Final Fantasy XI is to follow in the footsteps of the likes of City of Heroes, Age of Conan and EverQuest II by offering a "buddy" system that will allow characters of very different levels to play together effectively.
Called Level Sync, the system will allow members of a party to "power down" to the level of a designated player. The stat bonuses from their equipment will also scale down appropriately, so you won't need to switch into low-level gear to join your newbie friends.
Square Enix promises that the system has been designed to avoid abuse by power-levellers and gold-farmers.
For more (frankly, exhaustive) detail on Level Sync, coming to FFXI in the next version update, check out the official development notes.