LobbyEssentials is a plugin that will turn any of your bukkit worlds into a lobby.
Download and install the plugin to your server. Verify that the plugin is working correctly, by running /lobbyess. Teleport to your lobby world, and type: /lobbyess setworld. The default world is: "world". Use the commands or change the config to your likeing.
It's really complicated.
lobby: chat: disabled: true // true: Players can't talk .. false: Players can talk .. Default: true disabledmsg: '&7[&cLobbyEssentials&7]&c You can''t chat here!' build: disabled: true // true: Players can't build .. false: Players can build .. Default: true disabledmsg: '&7[&cLobbyEssentials&7]&c You can''t build here!' hunger: disabled: true // true: Players get can't get hungry .. false: Players can get hungry .. Default: true falldmg: false // false: Players can't take any damage .. true: Players can take damage .. Default: false | Applies to all types of damage, not only fall damage. world: world // The world's name. Default: world