"Popular open source software such as Drupal, Joomla!, and Plone
are provided for free, but the greatest advantage comes in the form
of increased flexibility and total control over customization of
the product. This allows you to develop a more tailored solution
for your organization's needs. But there's a catch: You have to
know what you're doing.
"While these types of open source solutions are a great choice
for organizations that have highly technical staff or the financial
means to hire outside developers, organizations with little
in-house IT resources might find the learning curve too steep and
the lack or “formal” support a bit disconcerting."