12 Essential Plugins that Extend WordPress as a CMS
This article covers the plugins mentioned by vteixeira, plus a few more.
I’m currently just using Pages as chunks of content (that is, pages-within-pages). But this is not ideal, as the pages I’m using as content blocks get added to the site as a separate, publicly viewable page, even though nothing links to them.
Maybe there is some way of using a custom post type instead?