These are many great resources that you find can find online for learning R. We provide the following list of resources along with their descriptions to help you in your path of learning this open-source and very powerful programming language and statistical software.
Base R Cheat Sheet - A cheat sheet of basic R commands.
R for Statistics 571 by Bret Larget - A good compliment to this course in that it is fairly short, it teaches the basics of R, and allow you to learn of the statistical applications of R such as statistical tests, bootstrapping methods, and data visualization.
R-bloggers - This website compiles the blogs of many data analyst who share the cool work they do with R! This source is good for seeing the potentials that R has for data analysis and visualization. You will see a diverse set of interesting projects that are possible with many of the techniques that you learn in this course.
UCLA Statistical Consulting Group - This website provides excellent references and and a library of resources for R. The collection of resources and tutorials can be somewhat advanced, but it is a good reference to keep for when doing projects.
And most importantly...
Google - Google searches can be very helpful in redirecting you to specific resources, often times it will be your best friend!