This is the application used for a class on Ruby on Rails based around a travel agency that books cruises for its customers. You can find the practicals explaining the steps to build this app at: http://homepages.abdn.ac.uk/b.scharlau/pages/teaching/CS5550/practicals/
The goal of this practical is to move beyond simple apps to one, which brings a variety of aspects together so that the participants experience the breadth and variety available in Rails applications.
By the way, some of you might recognise this app as being based on the travel agent example from the O'Reilly Enterprise JavaBeans book. This is, indeed, a take on that old scenario.