Xaquín G.V. has a dead simple tutorial on how to make a choropleth map with open source QGIS.
A Choropleth in QGIS
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Second Edition
Visualize This: The FlowingData Guide to Design, Visualization, and Statistics (2nd Edition)
Visualize This: The FlowingData Guide to Design, Visualization, and Statistics (2nd Edition)
New tools, refined process.
