nesta (rubygems): Nesta is a lightweight Content Management System, written in Ruby using the Sinatra web framework. Nesta has the simplicity of a static site generator, but (being a fully fledged Rack application) allows you to serve dynamic content on demand.  Content is stored on disk in plain text files (there is no database). Edit your content in a text editor and keep it under version control (most people use git, but any version control system will do fine).  Implementing your site's design is easy, but Nesta also has a small selection of themes to choose from. 
Keywords: cms|file-based-cms|haml|markdown|ruby|sass|sinatra|sinatra-application|ssg|static-site-generator|textile