What are some examples of natural selection in action?

In humanity, it's called the Darwin Awards.

The Galapagos islands, birds that migrated from Africa to Madagascar when they where closer to each other, when Madagascar began to drift away, the birds had to change to suit their new environment. Madagascar did not have many small, grainy seeding plants growing on it, but rather more things like Coconuts and other thick-shelled nuts. as a result, birds with thicker, stronger, shorter beaks where more likely to survive and thus had more offspring. That trait continued to grow more and more prevalent, until you had what appeared to be a totally unrelated species to that of the original African finch.