Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
Drupal is an excellent free software content management system, written in PHP. It's a good choice if you have to build a new site for non-technical users or customers, as both content editing and site administration can be done directly in the main site by authenticated users, and there's very little markup for those users to learn.
I'd investigated and deployed several different content management systems before discovering Drupal. For me, the best thing about switching to this particular CMS was that you can create templates that use only CSS for layout, rather than tables, and the application itself doesn't fill your CSS layouts with tables either. Drupal has a very active community too.
Drupal runs well on Etch, and pretty much everything you need is already packaged in the Etch repositories. There's a Drupal 4.7 package in Etch, but to get the latest 5.2 release you'll need the version from Debian testing.