I have made several R packages to support my statistics teaching. These can be found below.
Johnson Neyman Plotting Tool for Conditional Effects
This is R package for students to plot conditional effects using the JN technique (via http://rpubs.com/bachl/jn-plot).
Skewness and Kurtosis
This R package calculates skewness and kurtosis for continuous variables in a manner that mimics SPSS.