How to define custom colors and color palettes in R and create your own scale_color and scale_fill functions to use in ggplot2.
Techniques in ggplot2 to make your plots more flexible and robust to changing data.
An introduction to the basic functions of the cowplot package for arranging plots together.
Fun and custom-looking alternatives to simple color legends in ggplot2.
Course materials for 36-315, a full-credit undergraduate course at Carnegie Mellon University on data visualization in R.
Slides from a useR group lightning talk on getting started with creating custom themes in ggplot2.