The 1.5 version of Xamarin Workbooks for Mac is available as a free download on our website. The program lies within Developer Tools, more precisely General.
From the developer:
Xamarin Workbooks provide a blend of documentation and code that is perfect for experimentation, learning, and creating guides and teaching aids.
You may want to check out more Mac applications, such as Xamarin Android Player, Xamarin Profiler or Xamarin Studio, which might be similar to Xamarin Workbooks.