I took a cue from Istvan and used gource to visualize six months of Bioconductor development here:
Leaf nodes are files. Other connected nodes are directories. The single central node (evident over time) is the root of the Bioconductor SVN repository. The files are being modified over time by the people flying in and out of the view. The "explosions" of new nodes/branches that occur are often new packages being added to Bioconductor.