Life On The Edge With Merb, DataMapper & RSpec
The book is written in Markdown comes complete with a set of rake tasks for publishing to HTML and plain text formats. run 'rake -T' from the root to see the options available (you will need to have BlueCloth installed, sudo gem install BlueCloth).
This work is licensed under a Creative Commons Attribution-Noncommercial 2.0 UK: England & Wales License.
Source code of the applications are dual licensed under the MIT and GPL licenses: