Many of our clients and colleagues have been migrating toward using versioning systems to manage the development of their websites and their clients' websites. Advantage Labs uses an open source version control software system called Subversion.
Advantage Labs is a firm believer in maintaining "version control" of its managed sites. A software called Subversion allows us to set up a system for "checking out" sites from the server to make changes (experimenting with new modules for example) on a local computer without affecting the live site. Then, if and when the changes are deemed ready for the live site, the changes can be "checked in" back to the server with a log containing notes about the changes.