Several text books either use ggformula or have accompanying documentation that demonstrate how to use ggformula.
Foundations and Applications of Statistics: An Introduction Using R (R Pruim, second edition) is an R-infused probability and mathematical statistics text that emphasizes connections between probability and statistics. The first edition of the book predates the ggformula package, but the the second edition is supported by the fastR2 package and uses ggformula for plotting.
Introduction to the Practice of Statistics in R (NJ Horton and BS Baumer) describes how to undertake analyses in R that are introduced as examples in Introduction to the Practice of Statistics, by David Moore, George McCabe, and Bruce Craig.
OpenIntro Stats now has versions of their labs designed for use with the mosaic package.
The mosaic labs were adapted by Ben Baumer and Galen Long of Smith College and updated to ggformula by Bonnie Lin and Nicholas Horton of Amherst College.