One place for helpful ECMAscript 2015 (ES6) stuff

(remember, ES2015 === ECMAScript 2015 === ES6 === ECMAScript 6)

Good Resources

ECMAScript 2015 Language Specification--official

Babel's Learn ES2015

Babel's ES2015 "Try it out"

ES6 Compatibility Table

Airbnb Style Guide

Good Articles

How to Learn ES6

This one ^^ has links to more great resources, some that cost $, others that don't.

Top 10 ES6 Features Every Busy JavaScript Developer Must Know