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.
Xfiles is an interactive utility for comparing and merging one file tree with another over a network. It supports freeform work on several machines (no need to keep track of what files are changed on which machine). Xfiles can also be used as a cross-validating disk<->disk backup strategy.
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.
cvs-importer automates the task of importing all past versions of an existing project into CVS or Subversion, including automatically removing generated files, creating .cvsignore files/svn:ignore properties, and tagging each version. Thus, you can gain some of the advantages of scm for the older versions that weren't actually developed in cvs/svn, by having all the changes in the history.
cvssh is a solution for securing a CVS pserver. The CVS pserver option is a useful but insecure tool for managing CVS repositories. Most approaches to securing CVS either involve ssh tunneling or avoidance of pserver altogether. The cvssh program offers a third alternative, which combines the simplicity of ext on the client with the flexibility of a pserver-based repository.
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.
The P4DTI connects your defect tracking system to the Perforce configuration management system, so that you don't have to switch between them and enter duplicate information about your work. It also links changes made in Perforce with defect tracker issues, making it easy to find out why a change was made, find the work that was done to resolve an issue, or generate reports relating issues to files or codelines.