Revision Control System

CS-RCS
Inexpensive graphical RCS for Windows 95/NT, free for individuals, includes free standalone CSDiff. (ComponentSoftware)
http://www.componentsoftware.com/csrcs/

GNU RCS
The GNU Revision Control System, a popular free SCM tool on the UNIX platforms.
http://www.gnu.org/software/rcs/rcs.html

Purdue RCS Development
Contains UNIX, Windows and DOS distribution files and source, contributed software, support, and documentation.
http://www.cs.purdue.edu/homes/trinkle/RCS/

RCE: the Revision Control Engine
Designated successor to RCS. Offers VRCE, Java based graphic user interface, and Byte Differencing Engine, efficient delta revision storage that supports all data types. API enables integration into any electronic data management system.
http://www.aicas.com/rce.html

RCS Tutorial - the Revision Control System
Frames-based short HTML online tutorial, by David L. Spencer.
http://www.csc.calpoly.edu/~dbutler/tutorials/winter96/rcs/

Walter F. Tichy's Home Page
Professor of Computer Science at the University Karlsruhe, Germany, creator of RCS. Some pages in English, some in German, including two talks on software configuration management.
http://wwwipd.ira.uka.de/~tichy/