MongoDB: A superb NoSQL database, MongoDB has risen in popularity with companies who use large volume data sets. MongoDB also works well with Rails apps and is the default database for the Meteor.JS project. It is growing much faster than any other NoSQL or SQL database, such as Cassandra, CouchBase, MySQL, SQLite, etc.
Express: Express.JS is a node application framework, and makes it very easy for developers to create an MVC application on the server side.
Not only can you create routes and templates with ease, but support multiple template languages such as Jade.
Angular JS: More of a framework to create SPAs than a typical language when it comes to web development, Angular.JS is extremely important and has seen a lot of money being poured into it by Google and YouTube over the years. It is growing much faster than EmberJS and Backbone.JS.
Node JS: Although it runs on Linux, Node.JS is actually a server based on the Google V8 engine. A lot of developers swear by its non-blocking I / O which allows it to deliver millions of requests with ease. LinkedIn, after turning to Node.JS for their mobile app, were able to reduce server count by almost 90%, while delivering 20% faster results.