git
Git is a source code management system that features distributed storage and emphasizes speed and data integrity.
Git allows multiple users to work on a project simultaneously and keep their files up-to-date with each other. The "distributed" aspect of Git means that instead of having one central repository, like with SVN, that users push to and pull from, everyone has a local copy of the repo, making their changes as needed, and can update the central copy so others can be in sync. One advantage of this system is that it makes the repository robust against failure of the central server's data storage mechanism (or failure of any local copy for that matter). Changes can also be made and committed offline and later simply pushed to the server. Git also keeps "snapshots" of the repository, allowing for a rollback to a stable version if something were to irreparably corrupt the latest branch of the repo.
