I joined Stack Overflow almost two years ago now, and it's been an invaluable tool for both teaching and learning. Though my activity has declined recently, I've been active on other Stack Exchange sites; most notably, I've been an active participant on the Anime & Manga Stack Exchange, which is currently in beta.
With beta sites, we want to make sure that the site is headed in the right direction. Higher visit counts, more avid users, and all that, so that the site can successfully graduate from beta and become a full-fledged member of the Stack Exchange community.
Previously, to track these stats, we used a meta Stack Exchange thread which required manual updating. Because most of the process was straightforward, I decided last August to automate it.
The result is Stacker. Originally, it tracked only this one site, but because most of the stats come from a single page (the Stack Exchange site index), I decided to track all of the sites, keeping them indexed by their site ID.
For example, here's a look at a few of Stack Overflow's statistics from Feb 3, 2014:
You can check out the project below, or view the source code at the second link. At the time of writing, I have not published the data crawler source, but I'm working on making it presentable in order to do so.