Ruby

Rails 5 adds ability to create module and class level variables on per thread basis, Rails 5 disables autoloading after booting the app in production и Quiet assets in Rails 5
Examining The Internals Of The Rails Request/Response Cycle, Good Module, Bad Module и Abstract Class Pattern in Ruby
Resumable File Uploads in Ruby, Managing ActiveRecord connections with Octoshark и Elixir for Rubyists

JavaScript

JerryScript 1.0, JavaScript Garbage Collection Improvements — Orinoco и In Defense of Douglas Crockford
JS MythBusters — an optimization handbook from a high level point of view, Mobi.css — a lightweight, flexible css framework that focus on mobile и Spectre.css — a lightweight, responsive and modern CSS framework for faster and extensible development
Cesium — an open-source JavaScript library for world-class 3D globes and maps, Granim.js — create fluid and interactive gradients animations with this small js library, Anim8js — animation library for javascript и Linkify is a JavaScript plugin for finding links in plain-text and converting them to HTML tags