This app uses the Twitter streaming API to track and display (in a map and a stream) selected Twitter users. At the Seattle Times, we're using it to respond to May Day festivities.
While developing, you need two Bash shells. One to run Grunt, and another to run the index.js file that actually subscribes to the firehose. You'll also need to get access tokens from Twitter and load them into your auth.json file. Not for the faint of heart.