AngularJS - AngularJS lets you extend HTML vocabulary for your application. The resulting environment is extraordinarily expressive, readable, and quick to develop.
Backbone.js - Give your JS App some Backbone with Models, Views, Collections, and Events
jsPlumb - jsPlumb is an advanced, standards-compliant and easy to use JS library for building connectivity based applications, such as flowcharts, process flow diagrams, sequence diagrams, organisation charts, etc.
ExpressJS - Sinatra inspired web development framework for node.js -- insanely fast, flexible, and simple