Library Enforce is a Bukkit plugin that helps to make your server as quiet as a library by telling users who are spammy to kindly shut up through a warning system.
If you want to contribute to Library Enforce, submit a pull request and your code may get included in the plugin. If you find any bugs please report them to the bug tracker.
Library Enforce requires the latest version of CraftBukkit which is available for download here.
The plugin is currently coded and hopefully tested to work with CraftBukkit version 1.3.1-R1.0.
Special thanks to ammaraskar and mbaxter (from joe.to) for allowing me to use their thread safe permission check.