Here’s a great idea well executed – MapOnShirt uses OpenStreetMap data and some nice custom styling – and an easy-to-use website, to allow you to design your own T-shirt of anywhere in the world. It works best in large built-up places, particularly across new-world cities with their grid structures and other large-scale planned road topologies, but familiar shapes in older cities work too – such as the River Thames.
MapOnShirt was kind enough to create a mock-up of a shirt for the recent Street-O race in London that I organised. I reckon these kinds of shirts would make for great prizes for such events.