Choosing a CMS?

I’m looking for an open source PHP/MySQL CMS that I can use as the backend to my website.

My site consists of multiple quasi-independent sections, each with its own subdomain, that should be able to function as seperate sites. The range in style from blogs to articles to file libraries, but all share a consistent global menu system, footer text, 3-column layout, et c.

I’ve looked at PHPNuke, just because that’s the only thing that jumps to mind, but I want to make sure I’m not missing anything before I dive in with it.

What are your suggestions? Is there anything better than PHPNuke for this type of thing out there?