Bukkit

MeltDown hides you from the players and in the TAB list too.

El.Mob disables some monster abilitys like the teleportation of endermens or the explosion damage of creepers.

SafeGuest disables the most abilities of guests like building or something.

LingoRevision changes the messages to your preferred language you choose.

DisableMessage disables the join, quit and death messages.

RulesAhoi equips you with the best rule questioner.