Bukkit

Commands:

/Lock | Lock / Unlock the server (Toggle)
/Lock on/off | Lock / Unlock the server
/Lock on time m/h/d | Lock the server for certain amount of time (m is for mintues, h is for hours, d is for days)
/Lock Help | Display the list of commands
/Lock setLockedMotd Motd | Set the Motd wich will be displayed when the server is locked
/Lock setPrefix Prefix | Set the prefix of the plugin ( This Prefix will be displayed in every message after a command is executed)(Note: You can set the prefix to two words from in-game)
/Lock setKickMessage Message | If a player joins while the server is locked, this message will be displayed
/Lock LockedMotd on/off | Enable / Disable the LockedMotd