It would be helpful if each of the source tree directories had a file in that directory that described the purpose and use of the source in that directory. This would serve as an educational roadmap for anybody browsing the tree (particularly useful for people using viewsvn). The information should give a high level overview of the component/subsystem implemented by the code in that directory. The files should NOT list each of the individual files, since that information all to easily becomes obsolete. The information in the descriptive files should be the type of information that generally does not grow stale quickly.