Rmuflow-mockups is a project mainly written in Ruby, it's free.
These mockups were generated by Nanoc, a static site generator
Using blueprintcss stylesheets + BP-Vertical-Positioning plugin (see content/styles)
And slim templating language (see layouts)
gem install adsf
cd output && adsf
to start the web serverYou can simply view the mocks standalone by opening the html files under output in your browser.