Much of the richness of digital storytelling is due to the use of a wide range of images as an integral component of the narrative. There is, however, a type of image essential to education that is underrepresented in many of the current digital storytelling projects. This class of images could be called "analytical images" - images that are structured in such a way as to enhance the systematic investigation of a subject. These include - but are not limited to - graphs, charts, diagrams, and maps, a group described by Philip Morrison as "cognitive art". Unfortunately, these tools are used in much of education in an excessively compartmentalized and narrow fashion that negates their broader expressive potential. Thus, while graphs are used in math class, diagrams in biology class, and maps in geography class, very little is done in terms of teaching students how to conceptualize any of these tools as interrelated members of a wider set of tools for thinking. Some of the materials detailed below might help remedy this situation.
The best sources I have found for clear thinking about analytical images are offline. I would recommend starting with a trilogy of books by Edward R. Tufte: The Visual Display of Quantitative Information, Envisioning Information, and Visual Explanations. Rather than focusing on the technical details of a particular graphical tool for the presentation of information, Tufte develops a rigorous theory of communication via analytical imagery. The first volume in the trilogy is probably the most important - the basic components of Tufte's theory are laid out here, from the identification of those elements that interfere with visual communication (e.g., the commonly encountered forms of visual clutter that he terms "chartjunk"), to those that promote it (for instance, ways of optimizing the data to ink ratio). The second volume extends Tufte's thought from the realm of quantitative information into a broader sphere of concepts to be represented, including spatial, chronological and part-to-whole relations. Volume three in turn places these concepts within the context of their use in narrative and evidentiary contexts. It is important to keep in mind that Tufte's theories can (and should be) thought of separately from the specific examples he proposes - in most instances the examples only represent one particular instantiation of some of his principles, and not a general set of graphical design dictates. In fact, translating Tufte's thought from the printed page to the computer screen yields results that can look quite different from his examples.
Complementing Tufte's approach are three books from a specific subset of the cognitive arts - the discipline of mapmaking. While it might seem to run counter to the spirit of this commentary to highlight mapmaking by itself, these books are rich with implications and ideas that stretch well beyond their disciplinary confines. Additionally, they also embody a definition of mapmaking practice that is far more expressive than the "turn left at the gas station, then go for another mile and a half" images that are commonly evoked in educational contexts. Two books by Mark Monmonier - How to Lie With Maps and Mapping It Out: Expository Cartography for the Humanities and Social Sciences act as an outstanding introduction to the subject. The first, despite its ironic title, spends at least as much time exploring how to use maps to communicate as it does warning about their possible misuse. The second book is an efficient guide to cartographic techniques, accessible to even the least experienced mapmakers, and rich in examples of the use of maps to visualize data, make arguments, and tell stories. As an added bonus, both of these books are available in inexpensive paperback editions. A final volume by Alan M. MacEachren, How Maps Work: Representation, Visualization, and Design, parallels Tufte's work in proposing a theory of maps that goes beyond a particular graphic practice, while developing a theoretical backdrop with applications to all uses of analytical imagery. The scope of MacEachren's work is outstanding, incorporating topics ranging from cognitive psychology to the theory of signs; while it may take more than one reading to digest all the material presented here, the effort will be richly repaid with original and powerful conceptual tools.
Having a strong set of conceptual tools is good; being able to bring this set into active practice via technological tools is even better. More later on software that does just that...