Several research groups around the world in the area of mobility and transportion optimization are exploring the use of a particular slime mould, Physarum polycephalum (the "many-headed slime"), to establish the most efficient routes around congested cities and countries.
The moeba-like creature forages for food by sending out branches (plasmodia) from a central location, with a speed of approximately 1cm per hour in optimum conditions. Even though it forms long, sprawling networks, it biologically still remains a single cell. As the creature uses its tentacles to explore for nearby food sources, and then thins out those part that do not contribute, it is able to find the most effective way of linking together scattered sources of food, or even find the shortest path through a maze.
As a by-product of this biomimicry-inspired optimization, it also creates some intriguing physical maps.
Several more detailed news articles on this research method are available at The Guardian, New Scientist and Discover Magazine. Alternatively, the academic paper "Rules for Biologically Inspired Adaptive Network Design" can be found here.