Bukkit

 This plugin provides a single command for most management tasks for worlds; have a quick look at the synopsis for supported subcommands:

 world list
 world create [<options>] <name>
 world load { -a | <name> }
 world unload [-n] {<name>|<uuid>} [...]
 world control {<name>|<uuid>} { all | {<property>[=<value>]} [...] }
 world save { -a | {<name>|<uuid>} [...] }
 world switch [-c | -p <x>,<y>,<z>] {<name>|<uuid>}

This plugin is designed to intentionally bypass some internal limitations of Bukkit, CraftBukkit or Minecraft, so it is server operators' responsibility to set values that make sence, unless you really want to break your world or server; because of that, be very careful when granting permissions of this plugin to others.

Please note that some features require Minecraft Forge (thus, Cauldron, or its derivative), however the plugin itself should be compatible any server software that implemented Bukkit API.

Subcommands

   list

    This will list all currently loaded worlds with name and UUID. If Minecraft Forge is present, the world provider name will also be shown, as long as all unloaded worlds that available for loading.
    Example on Spigot and Glowstone:

     > world list
      Loaded worlds:
       world (6b32b92e-9346-41da-85eb-039bdbffeea7)
       world_nether (6bccd796-9f52-49de-9182-623351ac8314)
       world_the_end (5d07dd3f-4db4-4d24-9daf-112df647ac38)

    Example on Cauldron:

     > world list
      Loaded worlds:
       Overworld 'world' (2be19a1c-fafe-47ff-8337-a8f1fc84b967)
       Nether 'DIM-1' (cfa3d2ef-7fbe-466d-b636-1b2d1c2fa634)
      Unloaded worlds:
       the_aether
       The_End

   create

    Dynamically creates a world and load it. It uses standard bukkit API to create world so if the a world save is exist in save directory, the world will be loaded from file system; in this case, some but not all world settings (such as world seed) will be read from save, instead of command line options of this subcommand.
    See on-line usage message for more information.

   load

    This subcommand is available only if Minecraft Forge is present. It loads worlds that registered in Forge but currently unloaded. Use 'world list' for currently unloaded worlds.

   unload

    Unload a world. Note some implementations such as Cauldron may allowing you to unload overworld, but the server software will not functioning correctly after that; while some other such as Glowstone appear to be fine with overworld unloaded. Forge registered worlds can be loaded again using 'load' subcommand, 'switch' subcommand or in-game portals, so you may use it to unload currently unneeded worlds (but not overworld!) to save memory on Cauldron.

   control

    Display or change world properties.

   save

    Save one or more worlds to file system.

   switch

    Teleport yourself to another world. This command may only be used by a player to teleport themself into the specified world; if the world is currently unloaded but available from Minecraft Forge world registry, it will be loaded first.
    The default teleport destination is the spawn point of the world; option '-c' can be used to use current player position instead, inter-world movement factor (such 1:8 for Nether) is considered in this case; option '-p' can be used to specify a coordinate to teleport to.

Source code here: sourceforge.net