Very simple plugin to add a /spawn command to teleport the player to the world spawn location, and a /setspawn command to move the world spawn location to the player's current location.
Of course not just anyone can use these commands. They must be given to players with a permission system such as the official PermissionsBukkit. This plugin has the following permission nodes:
RevertedSpawn.spawn
- allows use of /spawnRevertedSpawn.setspawn
- allows use of /setspawn (defaults to op)