NodeJS - the best part about these javascript libraries is when you start learning them, they come pre-packaged along with node js - like their starter packs. That gives you a good idea on strength of NodeJS. I have personally been using Node for last 3 years and I have used Weblogic, webspher and tomcat in the past. I seem to love NodeJS.
RE: 5 Best JavaScript Stacks for your next Web Development project