This app collects trending Google searches, tweets, movies, Reddit and Instragram posts. I use this to keep track of current trends. You can try it our here:

Let there be flash light

This is a Rails app but there is a ton of fun stuff happening in the background. Every 5 minutes, a background jobs collects the latest trends from all across the web. After this, I generate a static page with this trends data on it. This static page is then uploaded to S3. Trends watch itself, just renders that S3 static page.