This is a great source for basic R functionality like importing and manipulating data.  It also has very helpful information on making graphs (see this page).  

A free online tutorial for learning basic R commands.  It runs through your browser and does not require you to install R.

Just getting started as an R user?  You can first try running R on QUBES Hub here, without installing anything.  Eventually, though you will want to install it on your own computer by downloading it here.  RStudio provides a friendlier interface for using R, and can be downloaded here.  Rstudio requires R to be installed, so start by downloading R.

Trying to customize plots in R?  This page from the Quick R site provides a great deal of information on customizing plot options, in a much more visual (and less terrifying) format than "?par"

swirl teaches you R programming and data science interactively, at your own pace, and right in the R console!

For teachers:

swirl is a platform for teaching R programming and data science. However, an educational platform is only as good as the content it delivers to students. Although we have contributed some content ourselves, swirl is designed in such a way that you can create your own interactive content and share it freely with students in your classroom or around the world.

by Sharon Machlis
edited by Johanna Ambrosio

Computerworld