For keeping up with the stuff I use at work, SCCS fits the bill. (or the build ;-) No real setup required:
mkdir SCCS; sccs create filename
sccs edit filename
sccs delget filename
For formal stuff we use Rational Apex and PVCS (as appropriate). But for the maintenance of day-to-day scripts and data, it's SCCS. At home, I use CVS just 'cause it's on the BSD system, but it's frankly a lot harder to set up for personal files.
Once on a system where sccs had not been installed, I cobbled together a system from diff, ed and shell scripts.
The user soon to be known as criglerj