Node.js is typically used for servicing web applications, but it has found some other surprising uses as well. There's a fairly sizable robotics (check out Johnny-Five) and drone community around it as well. The programming editor Atom by Github is also a "traditional" desktop app with Node.js at the core.

In my opinion, Node's biggest advantage today is the absolutely massive module ecosystem that has sprung up around it in record time. It's already the biggest, as well as the fastest growing according to http://www.modulecounts.com/ You can find a package for almost everything imaginable, and your typical Node app is made up of dozens of these modules. So take a look at https://www.npmjs.com/, and try searching for whatever field interests you.