Javascript

Javascript lets you eval javascript code in game and basically create Bukkikt plugins in javascript!
The recommended way to use the plugin is to upload the javascript code to pastebin then run that. Heres a tutorial:
So you uploaded the javascript code to pastebin.com and have this link: http://pastebin.com/4N1V8WgP (this one will say "hi" 4 times to the server)
You take the text that is after the http://pastebin.com/ and copy that (it is 4N1V8WgP)
In the game you do /eval and then press ctrl+v and press enter
It just executed your javascript code!

You may also put the code into a book and quill and hold it and do /eval :P
The code is basically just like you would hopefully assume. It's all Javascript but you can access bukkit stuff like you would in Java. Read about the Rhino type of Javascript here

Command	Permission	Description
/eval <pastebin id>	javascript.eval	Eval Javascript code from pastebin.com
/eval	javascript.eval	Eval Javascript code from a book