I'm occasionally amazed to discover shops that don't use a version control tool. This is almost like finding someone who lives in a modern city but doesn't have an electricity hookup.
I started out with RCS and had a few minor reversions to SCCS. I've used a number of proprietary systems, over the years, but have never found them to be as usable as the open source stuff--first CVS and now SVN. I'd love to use SVK if I could use an Eclipse plug-in as convenient as Subclipse.
SVK
Some comments on using SVK for local work from a SVN repository
http://cwilliams.textdriven.com/articles/2007/02/16/svn-and-svk
http://scottstuff.net/blog/articles/2005/07/07/distributed-development-with-svk
http://octopod.info/2006/8/19/managing-multiple-local-mephisto-repos-with-svk
SVN
Switching from CVS to SVN
Guides
http://svn.collab.net/repos/svn/trunk/doc/user/cvs-crossover-guide.html
http://www.onlamp.com/pub/a/onlamp/2004/08/19/subversiontips.html
Instructions