Two good examples are regarding how you manage templates and use progressive enhancements with it. You just need a few lightweight pieces of JavaScript code to make it work perfectly.
I strongly recommend that you watch and read these articles:
- Video glass node
- Node.js YUI DOM manipulation
Pick up any language and try to remember how you would manage your HTML file templates and what you had to do to update a single CSS class name in your DOM structure (for instance, a user clicked on a menu item and you want that marked as "selected" and update the content of the page).
With Node.js it is as simple as doing it in client-side JavaScript code. Get your DOM node and apply your CSS class to that. Get your DOM node and innerHTML your content (you will need some additional JavaScript code to do this. Read the article to know more).
Another good example, is that you can make your web page compatible both with JavaScript turned on or off with the same piece of code. Imagine you have a date selection made in JavaScript that would allow your users to pick up any date using a calendar. You can write (or use) the same piece of JavaScript code to make it work with your JavaScript turned ON or OFF.