tag-trends is a web app that lets you visualize the popularity of Stack Overflow tags over time. Just enter a tag and you can see how many questions were asked about it each month.
Download / Install:
tag-trends is available at: http://sotagtrends.com
Runs in: Chrome, Firefox, Edge, and Internet Explorer (tested in IE11)
This app is written in TypeScript with Angular2.
To get the data the app has to lookup every single question and store it's tags in my own database. Due to the quotas on the Stack Exchange APIs it took a few weeks to collect all that data but now that I have it I just have a script that runs once an hour to pull in any new questions.
The source is on GitHub at github.com/robianmcd/tag-trends.