Inspired by the remarkable xkcd webcomic visual language, Michael Ogawa created a series of visualizations mapping collaborative efforts of various developers in a variety of tools and programming languages, such as Apache or Python.
Data comes from the project repository logs. Time flows horizontally from left to right. At each timestep (usually a month) developers are clustered by the files they modify. A histogram at the bottom shows the volume and type of file committed. You can mouse-over individual lines to see them better.
The two images shown here display the collaborations between developers of Apache (a popular webserver) during the first two years of planning and documentation of its 2.0 branch.