The Power of Content Management Systems
Drupal
At the moment I'm figuring out how Drupal works. I've also tried Joomla! and Mambo some time ago and it seems that Drupal is much more flexible. The user management capabilities are impressive. For more information about CMS systems, visit CMS Report.
Another advantage of Drupal, when compared to Joomla!, is that it's search-engine friendly out of the box. I mean by that that the links created by Drupal are easy for search engines to understand, resulting in more traffic to your website. With Joomla! it's much more difficult to make the links search-engine friendly. I'll keep you updated with my experiences with Drupal.
After experimenting this weekend with Drupal, I must say Drupal is very flexible and I like it a lot. I was able to install it without problem and I like it's simple, but powerful administration interface. It's a great tool to separate content from presentation. I like it more than Joomla. For video tutorials to learn Drupal in only 3 hours, visit this site.
Now that I know more about Drupal's category system, modules, theme's and so on, I must say Drupal is very impressive. If you want a site with communities, Drupal is in my opinion the way to go. The learning curve however is maybe somewhat steeper than Joomla, but as far as I know until now, Joomla has a much less impressive categorying system.
Wordpress is also a great tool used by many bloggers around the world. I have no experience with Wordpress yet, basically because I don't want a blog. However, it's worth mentioning here.
I found the following book very helpful while developing my site:
Look on my computer training books page for the best books about Drupal, Joomla and Wordpress. Look at the content management subpage.