When designing an API, it's important to follow several well-intentioned and reasonable principles. Check out this slide deck for a great overview of the different principles you should adhere to when developing an API! It covers everything from documentation to how you expose different services to how you communicate updates and version changes.
I was first exposed to Node.js during the HackNY hackathon, one of the largest student hackathons on the East Coast. My partner and I built an awesome news/media consumption web app that basically calls into about 10 APIs whenever you enter a search query, then returns a page aggregating results from all those sources. It was lots of fun and a surefire way to win a prize at the hackathon, and we won a prize for using the most number of APIs.
I needed a refresher on Node.js because I haven't touched it since, so I went and re-educated myself on the good stuff recently by reading some getting started guides and following along to create simple, barebones apps. Here are some links I found useful:
The dead-simple step-by-step guide for front-end developers to getting up and running with Node.js, Express, Jade and MongoDB - this one's written by someone who develops on Windows. So if you're always left scratching your head when someone writes about some tool that's only available on Mac, this one's for you. This combination of Node.js, Express, Jade and MongoDB is one of those modern stacks that the industry is increasingly using nowadays.
Creating a simple RESTful web app with Node.js, Express, and MongoDB - by the same author above.
The Node Beginner Book - I don't think this one's worth its $9.99 price. But for free, you get pretty much the first 1/3 of the book on that page I linked to and it does a good job covering the basics.