BikeGrid [gicentre.org] is a very sophisticated and data-rich visualization that provides a detailed overview of the actual performance of the Barclays Cycle Hire scheme. It shows the real-time and historical availability of the "Boris bikes", which are located in over 300 docking stations spread around central London.
The initial map view shows all docking stations (and proposed stations) as rectangles, sized by the capacity of the station. Darker stations are full, while lighter stations are empty. A unique "grid view" reveals the status of each docking station more clearly: the proportion of bikes at each station is indicated by the height of the blue bar. Very full or very empty stations are shown with a lighter or darker border respectively. In addition, the actual status of each bike station over the last 24 hours can be seen as a line graph, highlighting the urban dynamics of bikes going in and out the city centre over a time span of a typical day.