I’ve been spending a lot of time lately experimenting with the open-source Drupal content/blog management system, which has just reached version 5.0. It has a lot in common with WordPress, but it’s much more powerful and much more flexible. However, perhaps inevitably, it’s much more complicated as a result.
Probably the best starting point is to think of it as a blogging tool for multiple authors. The familiar tools of blogging are (generally) in the box to begin with: RSS, categories, comments, etc. If you want to extend your blogging-with-comments into a proper discussion forum, you can do that. If you want to offer distinct category lists (ie taxonomies), you can. If you want to have different types of pages for different uses, you can. And so it goes on. At first glance, there isn’t much in this space which it can’t do, as long as you’re up to the config task. It isn’t best-of-breed in any particular facet, but it’s a great way to tie it all together.
I’d still recommend WordPress for most low-level blog-style projects – which, in my experience, covers most things people actually would want to do. But if you do need to take things to a higher level, Drupal looks like an exceptionally good bet… if you’re prepared to get your hands dirty. A basic understanding of PHP should be enough to get you started, though.
Drupalsites.net gives plenty of demonstrations of Drupal in action, and it shows the huge variety of uses.