Bukkit

Later Version

Disallow dropping the head (or replace it directly by the backup-ed Helmet)
Disallow recovering the head (to disallow abuses of /give with this plugin)
GroupManager and/or Party support ?
Support Spout

Version 0.9

PlayerDisconnect events are now handled. If you leave with a HeadBlock on your head, it will be replaced by your old Helmet (or nothing if you had nothing).
Tested on CraftBukkit version 1.6.4-R2.0
Tested on CraftBukkit version 1.7.2-R0.2
Tested on CraftBukkit version 1.7.9-R0.2

Version 0.8

Many bugfixes and deprecation fixes
Now, you can only use the name of materials and not their IDs (same for data)
Tested on CraftBukkit version 1.6.4-R2.0
Fixed the UndoSelf and UndoOther

Version 0.7

Updated with latest CraftBukkit version 1.5.1-R0.2
Merged 0.5a and 0.6
Updated to Bukkit's Permissions system
Tested on CraftBukkit version 1.5.1-R0.2
Tested on CraftBukkit version 1.5.2-R0.1
Tested on CraftBukkit version 1.6.4-R2.0

Version 0.6

Not finished yet...you better use 0.5a still !
Disabled Permissions support until it's rebuilded with the new system
Structure to disallow abuses of the plugin to spawn items
Bugs fixed due to CraftBukkit update:
When the helmet backup is null makes the client crash when undo !
Crashes the client when placing AIR block

Version 0.5a

Various bug fixes, new stable version !
Tested with CraftBukkit 674
Tested with CraftBukkit 740
Tested with CraftBukkit 1.2.5-R1.0 (which fixes 2 crash bugs)

Version 0.5

Backup of old Helmet (use undoself or undoother to recover the old helmet)

Version 0.4

Added Permissions support (optional). If not installed, Operator status will work instead.

Version 0.3a

Blocks restrictions (items aren't allowed anymore since they have no visual effect)
Data restrictions (impossible values are not interpreted anymore)

Version 0.3

Data values (Color of Wheat for example)

Version 0.2

First Release (on Bukkit forums)