Vanilla List : The Vanilla Javascript Repository. A searchable repository of dependency-free JavaScript libraries. Over 100 projects and growing.
RequireJS : RequireJS is a JavaScript file and module loader. It is optimized for in-browser use, but it can be used in other JavaScript environments, like Rhino ...
TraceKit : Not all browsers support stack traces on error objects, but TraceKit squeezes out as much useful information as possible and normalizes it.