Here are a few practical applications of Node.js:
A Successful Web Front-End Refactor
Klout is a company that measures people's influence based on their activity in social media. We make use of their API at Table XI. Klout was powering a web interface to give users access to their scores with a LAMP (Linux/Apache/MySQL/PHP) stack. They found this was not scaling well as more users accessed the application. They rebuilt this interface using Node.js., and it's now handling tens of thousands of concurrent users on two servers.
Read more: "The Tech Behind Klout.com"
Etsy is using Node.js to push application data to Graphite to produce near real-time graphs of metrics such as login failures. They are using a daemon called StatsD to listen for messages, parse out the metrics, and periodically send the data to Graphite. Node.js' event-driven programing model lent itself well to this problem.
Read more: "Measure Anything, Measure Everything"
A Fun Example
NodeMap is a real-time app that displays messages from around the world on a map written by Vijay Rawat. It's a neat way to see Node.js in action.
Read more: Vijay Rawat on Github
Is Node.js for Table XI?
We're not currently Node.js, but we may find it useful for upcoming projects including an API integration with mobile apps.