I have developed a cheat sheet for R. Cheat sheets for R have become quite popular. If you’ve never heard of a cheat sheet before, it is a brief tightly laid out summary.
The cheat sheet I am working on, How Big is Your Graph?, explains some of the functions that can measure how big various aspects of your R graph are, such as the horizontal and vertical size of the plotting region and the height and width of your strings.
R Studio has some very nice cheat sheets on their website and I tried to model my cheat sheet after some of their examples. My cheat sheet is now one of the user contributed cheat sheets on that page.
I have some supporting information and extensions to the cheat sheet on my blog.
I might work on other cheat sheets. One that would take a lot of work, but would be quite valuable, I think, is a cheat sheet on date-time values in R.