Our society is producing digital information at an increasing rate: According to one estimate, in 2010 alone we will generate 1,200 exabytes—60 million times the content of the Library of Congress.
Information visualizations are one way to make sense out of that enormous amount of information. The human visual system is tuned to see patterns, spot trends, and identify outliers.
This article discusses the advantages and disadvantages of main types of information visualizations, with interactive examples. See full article here: A Tour Through the Visualization Zoo | June 2010 | Communications of the ACM
Another great source to learn more about visualizations are found here: 30 great visualization resources
and on the site Many Eyes where you can create your own information visualizations (for free).
The work by Edward Tufte became a must-read for people interested in information visualization.