Making instructor/student handouts in R
There was an excellent post on lukemiller.org about using R and knitr to make handouts/lab assignments/documents integrating R code, R output, and narrative text. Click that link to learn how to control what gets shown to whom. Besides being useful in this context, using R with knitr to produce easily readable/shareable documents that integrate code, output, and discussion is really handy for research, especially when communicating about analyses with collaborators (or communicating between grad students and advisors).
From the original post: "I teach some of my lab sections using R, and so I need to create lab handouts that include nicely formatted R commands and R output as an example for the students. These handouts will also include exercises where the students will be writing their own R code, or interpreting the results, or generating figures. For these exercises, it is useful to also have an instructor version of the handout so that I can recall what I was hoping to have the students do, and so that other instructors in the course have some clue as to what I might have been thinking when I wrote the exercises."