There are 633 open source (most are free) CMS systems
available. You could go here to see a list and compare
features (but I wouldn't recommend it ... too many choices ...
too confusing):
Some of these systems are truly amazing in their power
and functionality considering they're free. Many have
been installed hundreds of thousands of times and have
good support organizations and dozens (hundreds or
even thousands) of available plug-ins, extensions and
themes (most free as well).
Potentially a webmaster could prosper if you could put up new
Web sites faster and easier. Develop one site with CMS and you'd
be WAY ahead on future sites.
Which CMS is best? I really don't know. Here's four that
I think (for different reasons) have merit (and I'm sure
there's others):
Joomla (http://www.joomla.org/)
Druple (http://drupal.org/)
TYPO3 (http://www.typo3.org/)
CMS Made Simple (http://www.cmsmadesimple.org/)
All of these (and other CMSs) are more than an easier
way to create and maintain site content. All contain
(either natively or through extensions and plug-ins) built
in applications like event calendars, news archives,
shopping carts, forums, polls, help desks, photo galleries,
guest books, job postings, etc., etc., etc. These can
be used or ignored as the site's needs dictate.
Many are designed to be "community" sites where a
number of contributors (usually with different administrator
assigned privileges) contribute to the sites content creation
and upkeep. This is, of course, not a requirement if it was
a site that you alone were upkeeping.
If you have a specific requirement for something unusual
(let's say an employee expense reporting function), you
can use the link above link (http://www.cmsmatrix.org/) to
find which CMS systems have that function. I did the
"expense reporting" search and came up with at least 50
choices!
Interesting enough, you can test drive the above (and many
other open source CMS systems) without even installing
them on this site:
http://www.opensourcecms.com/