In a follow up to Visualizing Information for Advocacy, the Tactical Technology Collective recently announced Maps for Advocacy: An Introduction to Geographical Mapping Techniques.
The booklet is an effective guide to using maps in advocacy. The mapping process for advocacy is explained vividly through case studies, descriptions of procedures and methods, a review of data sources as well as a glossary of mapping terminology. Scattered through the booklet are links to websites which afford a glance at a few prolific mapping efforts.
While the example maps look very Googley and won't impress too many in the online mapping world, there are still some good links in there for data resources, terminology, and how maps play a role in displaying information.