The crowdflow blog has some beautiful visualizations of 880 iPhones moving across Europe from April 2011. They published the same data with 3 different colormaps, but they all look interesting.
Randall Hand
Randall Hand is a computer graphics programmer and news junky that's been working in the field for the last 15 years. He's responsible for visualizations generated on some of the most powerful supercomputers in the world, ytnef, mullion support in ParaView, and VizWorld.com.