TraceKit : Not all browsers support stack traces on error objects, but TraceKit squeezes out as much useful information as possible and normalizes it.
Tracery : A story-grammar generation library for javascript. Write grammar objects, get generative stories.
swfobject : SWFObject 2 offers two optimized Flash Player embed methods; a markup based approach and a method that relies on JavaScript & offers a JavaScript API ...
loglevel : Minimal lightweight logging for JavaScript, adding reliable log level methods to wrap any available console.log methods