Polymorphism and real world application

I am looking for some nice articles on polymorphism using real world applications (Finances, Web app, Sales, etc...).

I want to see and improve my coding practice, but I always believe in a nice real application, not in abstraction. It's my way to learn new things by the way.

I also have a new pile of cool new books, some are quite new, but nothing really too clever on the subject, except maybe the book I mentioned in an previous post.

So links are welcome :-)