ExpressJS - Sinatra inspired web development framework for node.js -- insanely fast, flexible, and simple
Sortd - Rated the #1 App for Gmail
Chart.js - Easy, object oriented client side graphs for designers and developers.
KanbanMail - A Kanban board for your emails.
Backbone.js - Give your JS App some Backbone with Models, Views, Collections, and Events
Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.