For serious websites with many different content, I'd go Drupal. The CMS' modular organization allows people with different specialities to focus on just one part of the site, without having to know what others are doing.
For a blog, I'd go either Wordpress or Dotclear, with a preference for the latter because it's much faster and doesn't wast resources like the former, which is especially important on limited shared hosting. There are blog engines lighter than Dotclear, but they're not as flexible. Think Textpattern.