Ask HN: How do you when to add a language to your skill set in resume?

Hi guys

I'll be going job hunting in a few months. How ever I'm a bit confused about the skill set I should list. I work with Python & Ruby mostly, have used C/C++ sometime back (univ stuff) and use Java for Android. But I'm reluctant to list Java under my skillset although I list Android (under platforms/frameworks), since my experience with Java outside of android is nil.

I've begun writing simple modules for Node.js (for fun) and have decided that I would list a language in my resume only if I've written some library/pkg for it or a significant app.

Curious as to what (self-laid)rules others go by when listing stuff under their skill set.

P.S: by 'significant' I mean popular or really useful/cool to show off.