MongoDB users interested in working with Node.js (or Node.js users looking at MongoDB) may find this tutorial from the blog at DigitalOcean to be particularly useful. It covers all the steps to connect Node.js to a MongoDB database on a VPS, and provides all the resources one might need to quickly catch up on either one.
The tutorial doesn't take it far beyond the basic set-up, but it will leave you with a Node.js application connected to a MongoDB database, which is enough to start exploring. Also, the instructions are detailed and code-supported such that it would be hard to get lost. Assuming you have some expertise in either Node.js or MongoDB, the tutorial looks like a good place to start for integrating the two.