I attended the Silicon Valley Perl Mongers (sv.pm) meeting tonight. The speaker was David Wheeler, one of the main developers of the Bricolage content management / publishing system. Bricolage was recently reviewed by eWeek and they loved it.
I'd heard a lot of good things about it, but never spent the time to look at it. After the presentation, I'm very impressed. It makes good use of existing technologies (mod_perl, HTML::Mason, PostgreSQL, etc) to build something very impressive.
The sick part is that I found myself wondering if it could be contorted into a sort of MovableType on steroids. I've convinced myself that it could be done with maybe a couple week's of hacking. So I'll put that on the list of "stuff to mess around with after the book is done".