Scripting in Java
I am a big fan of Python/Jython due to the clean syntax - which may suit you if you have some python experience. 
Otherwise Groovy which is based on Java syntax and may be an easier learning curve if most of your developers are Java guys. It also has the advantage of closer ties with the Java language and libraries. 
Beanshell is good if you have simple scripting in mind - it doesn't support classes. However I don't think it has had any support over the last few years (the JSR seemed to kill it off...) so is perhaps a bad choice if support is important to you.
Me and some friends are writing a MORPG in Java, and we would like to use a scripting language to, eg. to create quests.
We have non experience with scripting in Java. We have used Python, but we are very inexperienced with it. One of us also have used Javascript. 
What scripting language should we use?
What scripting language should we not use?