Radiant (<a href="http://radiantcms.org/" rel="nofollow">http://radiantcms.org/</a>) is very popular. If you want something more lightweight, I've just started using blogcast <a href="http://techoctave.com/blogcast/" rel="nofollow">http://techoctave.com/blogcast/</a> which is a great rails based blogging engine.<p>If you <i>really</i> want to learn Rails though, write your own CMS with it!