UUorld is an amazingly useful site that will help you explain a group of data in a very visual and understandable way that you may not be able to achieve simply by verbal explanation. The description below from UUorld's site explains it best:
"UUorld (pronounced "world") provides an immersive mapping environment, high-quality data, and critical analysis tools.
Great explanations are unfortunately scarce, but UUorld makes them easier to achieve through interactive four-dimensional maps. Our solution has three simple parts:
Draw on extensive, organized data.
Explore and grasp complex patterns through intuitive visual analytics.
Deliver new insight with compelling images and video.
We think you'll find four-dimensional mapping delivers results because the medium exposes the spatial and temporal context inherent to nearly all data."
See below for a small example showing population density in Illinois.