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.