Here's a little video demo'ing the Node.js integration module for Drupal. The module is for Drupal 7 only, and "It provides an API that other modules can use to add realtime capabilities to Drupal."
The demo shows triggers and actions which can distribute messages through a Node.js based service which pops up on all web browsers connected to a Drupal site. They indicate a future direction of implementing a chatroom on top of this.