Not all data visualization need color to clearly communicate and this interactive series of charts by the Federal Emergency Management Agency is an excellent example of how a simple monochromatic palette can be used effectively.
The Disaster Declarations for States and Counties map works extremely well - the denser the color, the higher the data point - although the zoom functionality is a bit of a nightmare if you're using a laptop trackpad.
It's great to see FEMA has opted to tabulate some simple data-points, too. Tables are often overlooked in data visualization in favor of some fancy-pants chart. If the table is simple with fewer data-points, it is amazing how much at-a-glance information they can communicate.
Finally, a message for my fellow Oklahomans. Don't get carried away with this lovely spring weather. According to the chart, FEMA mobilized in most Oklahoma counties in 2010 due to a severe ice storm. ;)