Locomotive is a simple but powerful CMS based on liquid templates and mongodb database. At my company ("NoCoffee":http://www.nocoffee.fr), we use it for our clients when they request a simple website.
If we have to give only 5 main features to describe our application, there will be:
We already developed a fully functional prototype in Rails 2.3.2 with both active record / mongomapper and it worked quite well. We are even using it for some client websites.
Now, our goal is to port our prototype to Rails 3 and migrate from mongomapper to mongoid. Besides, we put a lot of efforts to make it as robust as we can by writing better specs than we wrote for the prototype at first.
"Rodrigo Alvarez":http://blog.codecaster.es/ for his plugin named Congo which gave us a good starting point and for his availability for (very late) tech discussions.