Apache Subversion!

Mercurial is a free, distributed source control management tool. It efficiently handles projects of any size and offers an easy and intuitive command line interface. Mercurial efficiently handles projects of any size and kind.

Git for Windows focuses on offering a lightweight, native set of tools that bring the full feature set of the Git SCM to Windows while providing appropriate user interfaces for experienced Git users and novices alike.

Simple, high-reliability, distributed software configuration management. Fossil is a distributed version control system, bug tracking system and wiki software server for use in software development.

Darcs is an advanced revision control system, for source code or other files. It is fully distributed, and supports lazy fetching of the remote repository (fetching only what is needed at the time, rather than all history). It works best with text files, but it can also store binary files.

Team Foundation Server (commonly abbreviated TFS) is a Microsoft offering for source control, data collection, reporting, and project tracking, and is intended for collaborative software development projects. It is available either as stand-alone software, or as the server side back end platform for Visual Studio Team System. (VSTS)

An open source, distributed version control and bug tracking system for Windows, Mac OS X, and Linux.

EasyGit is a wrapper for git, designed to make git easy to learn and use.

The Perforce Software Configuration Management System features comprehensive SCM capabilities built around a scalable client/server architecture. Users can access the Perforce Server through a range of Perforce client software. Perforce can be deployed quickly and easily, and requires minimal administration even for large or distributed sites. The Perforce Visual Client, P4V, provides a graphical interface on Windows, Mac OS X, Linux, Solaris and FreeBSD. It includes a built-in merge feature, as well as Perforce's revision graph and Time-lapse View tools. »

monotone is a free distributed version control system. It provides a simple, single-file transactional version store, with fully disconnected operation and an efficient peer-to-peer synchronization protocol. It understands history-sensitive merging, lightweight branches, integrated code review and 3rd party testing. It uses cryptographic version naming and client-side RSA certificates. It has good internationalization support, runs on Linux, Solaris, Mac OS X, Windows, and other unixes, and is licensed under the GNU GPL. »

Source Control, Version Control and Bug Tracking