Front-end Web Development
Backend Web Development
NodeJS is good at handling a bunch of concurrent users at one time which makes it really powerful if you are building web applications. If your goal is to build a marketing site then NodeJS might be too much.
Since NodeJS was created, a couple of frameworks have come out, Express and Meteor, that make building web apps with NodeJS incredibly easy. Express has become that standard when building web apps with NodeJS and has already created the parts of a web app that you would recreate every time you start a new project. Meteor is built on top of Express and has created some really powerful features, like live page updates, for web apps.
Native Mobile App Development
Desktop App Development
Arduino, Raspberry Pi and Spark Core Development
IO plugins have been made for Johnny-Five that make it work for Raspberry Pi and Spark Core. Raspberry Pi is similar to Arduino, they just approach hardware and software in their own way. Spark Core is similar to Arduino, but take a cloud based approach to the industry. All three are incredible and be something that every developer should look into.