Version 1.x.x
I did some looking around on the server mods to find that there was no simple, lightweight, and easy-to-use invisibility plugin out there. So I made one. SimpleConceal is a lightweight, easy-to-use plugin for invisibility in a bukkit server. SimpleConceal uses two permission nodes and easy to remember commands to control who can and cant go invisible.

Features
1) Permission Support (else defaults to OP)
2) Suppresses OnJoin and OnExit messages when the player is invisible.
3) Config file for event handling.
4) Remembers invisible players (if in the event a server crashes, or someone dc's)
5) Allows the command sender to set someone else invisible or just themselves.
6) Can now remove offline players from the invisibility list.

Installation Instructions
1) Drop the SimpleConceal.jar into your plugins folder.

Thats it!

Commands and Explanations
- /simpleconceal (or) /sc - Shows plugin info.
- /simpleconceal list (or) /sc list - Shows the list of all currently invisible players (Online and Offline).
- /simpleconceal help (or) /sc help - Shows all available commands (Does not show aliases).
- /invis (or) /invisible (or) /hide - Sets the player using the command invisible.
- /vis (or) /visible (or) /unhide - Sets the player using the command visible (Works for Offline Players [Case Sensitive])..

In addition to these commands you can give it a parameter to set another player invisible or visible. In example: /invis Spartan_V23 (or) /vis Spartan_V23. All of these commands work in the console.

Configs and Example Config
With the 1.0.2 update, we added in a configuration file. Below I will tell you what each one does as well as show you the config file in the event one doesn't auto-create for you.

no_pickup - Stops the invisible player from being able to pickup dropped items.
no_item_drop - Stops the invisible player from being able to drop items.
no_block_break - Stops the invisible player from being able to break blocks.
no_block_place - Stops the invisible player from being able to place blocks.
no_player_interaction - Stops player interaction with toggle-able items. (doors, chests, etc).
no_entity_targeting - Stops mobs from targeting invisible players.
suppress_on_join_message - Suppresses the on join message for invisible players
suppress_on_join_message - Suppresses the on quit message for invisible players

#Do not edit the version number. It will cause errors.
version: 1.0.3

#The configs and messages below are for invisible players only.
configs:
  no_pickup: false
  no_item_drop: false
  no_block_break: false
  no_block_place: false
  no_player_interaction: false
  no_entity_targeting: false

messages:
  suppress_on_join_message: true
  suppress_on_quit_message: true

Permission Nodes
simpleconceal.list - Allows the player to list all currently invisible players (Online and Offline).
simpleconceal.allow - Allows the player to set self invisible and set self visible.
simpleconceal.allow.other - Allows the player to set another player invisible and another player visible.

Todo
1) None

!! Suggestions are always recommended. !!

Changelog

Version 1.0.0

Release

Version 1.0.1

Fixed Error: Could not pass onPlayerJoin to SimpleConceal

Version 1.0.2

Added Command: /simpleconceal list
Added Command: /simpleconceal help
Added ability to use commands in console
Added Config File for flexibility
Added permissions for new commands

Version 1.0.2 [FIXED]

Fixed Error: Could not pass EntityTargetEvent to SimpleConceal.

Version 1.0.3

Fixed issues with the permissions
Began minor optimization of code for efficiency.

Known Issues
1) None