This post is a continuation of the Creating Interesting Visuals series - click here to read the previous post on Radial Charts
Calendar heat maps are good for an initial look for potential seasonality and similar trends. They make a nice first exploratory step that you can then dig into more via more traditional line and bar charts.
What we can easily notice from this is that dba, gis, and stats all are primarily used on weekdays. This highlights their use as a professional resource. RPG by contrast has its activity spread into the weekend, which makes sense for a hobby site. GIS had a significantly more active second half of the year. DBA seems to have a similar occurrence, but this requires further visualization.Creating Interesting Visuals is continued here - Creating Flow and Chord Charts