Subversion is a version control system. Originally designed to be a compelling replacement for CVS in the open source community, it has far exceeded that goal and seen widespread adoption in both open source and corporate environments. The Subversion project produces Subversion's core libraries (written in C), a fully functional command line client (svn), repository administration programs, API bindings for various languages (Perl, Python, Java, Ruby, etc.), and various additional tools and scripts.
ViewVC (formerly known as ViewCVS) is a Python/CGI-based system for viewing and interacting with Subversion and CVS repositories through your Web browser. It can browse directories, view changelogs, generate diffs, view arbitrary revisions, and display annotated ("blame") listings. It has full support for tags and branches, and contains a database-backed query system like Bonsai. It was initially based on the cvsweb work by Henner Zeller, but has been ported to Python and dramatically enhanced.
reposurgeon is a tool for editing version control repository history. It enables risky operations that version control systems don't want to let you do, such as editing past comments and metadata and removing commits. It works with any version control system that can export and import git fast-import streams, including git, hg, bzr, CVS, and RCS. It can also read Subversion dump files directly and can thus be used to script production of very high-quality conversions from Subversion to any supported DVCS.
Meld is a visual diff and merge tool. It integrates with most version control systems. The diff viewer lets you edit files in place (diffs update dynamically), and a middle column shows detailed changes and allows merges. The margins show location of changes for easy browsing, and it also features a tabbed interface that allows you to open many diffs at once.
Conary is a distributed software management system for Linux distributions. It replaces traditional package management solutions (such as RPM and dpkg) with one designed to enable loose collaboration across the Internet. It enables sets of distributed and loosely connected repositories to define the components which are installed on a Linux system. Rather than having a full distribution come from a single vendor, it allows administrators and developers to branch a distribution, keeping the pieces which fit their environment while grabbing components from other repositories across the Internet.
Diffuse is a graphical tool for comparing and merging text files. It can work with many revision control systems as a diff viewer or merge tool. Diffuse is able to compare an arbitrary number of files side-by-side (n-way merge), and gives the user the ability to manually correct line matching and directly edit the files.
Bazaar is a simple decentralized revision control system. Decentralized revision control systems give users the ability to branch remote repositories to a local context. Users can commit to local branches without requiring special permission from the branches that they branched from.