Web CMS

Hi all,
I've been tasked with making a CMS recommendation for a fairly
high-traffic website, or possibly multiple websites.  The problem, of
course, is that I know absolutely nothing about CMS systems :)

So, most CMS systems that I'm aware of seem to want to control both
content management _and_ content delivery.  The delivery part needs to
be separate -- there will be at least one Rails front end, and the
view templates will contain container elements that we expect to fill
by calling out to a CMS system.  It'd make it really nice if the CMS
system would publish content to the filesystem and let us determine
where that content goes, making it transparent to the Rails app.  I'm
not even sure what the correct term for this style of CMS is (if it
has one), which would help my Googling.

The company in question doesn't have heavyweight CMS needs.  They need
to be able to do live previews, some basic auditing and versioning,
I18N, and scheduled based content updates.  Some lightweight workflow
would be gravy but not necessary.  And they're really looking for
something that's free as in beer...

Any recommendations?

---------
Brandon Byars
http://brandonbyars.com