Personally I was interested in seeing how much different committers have contributed to projects. For example, Linus Torvalds and Git: http://tomiaijo.github.io/github-treemaps/#/repository/36502... .

Also it is quite interesting to see the different programming languages used in projects. For example, Git has almost as much Bash scripts as C code: http://tomiaijo.github.io/github-treemaps/#/repository/36502... .