Kristopher Magnusson's "Interpreting Cohen's d effect size"

Kristopher Magnusson (previously featured on this blog for his interactive illustration of correlation) also has a helpful illustration of effect size. While this example probably has some information that goes beyond an introductory understanding of effect size (via Cohen's d) I think this still does a great job of illustrating how effect size measures, essentially, the magnitude of the difference between groups (not how improbably those differences are). See below for a screen shot of the tool.

http://rpsychologist.com/d3/cohend/, created by Kristopher Magnusson