Dave's Adventures in Business Intelligence

Really good read, in my opinion. Here’s the opening paragraph:

Almost all data visualizations are multivariate (i.e., they display more than one variable), but there are practical limits to the number of variables that a single graph can display. These limits vary depending on the approach that’s used. Three graphical approaches are currently available for displaying multiple variables:

• Encode each variable using a different visual attribute
• Encode every variable using the same visual attribute
• Increase the number of variables using small multiples

In this article, we’ll consider each.

The Perceptual and Cognitive Limits of Multivariate Data Visualization

If you don’t follow Stephen Few, it’s worth the few moments of your time to go have a look.