Official Blog

R-fiddle lets you run and write R in the cloud, all in the comfort of your own browser. Play around with R code in the your own browser.
Quandl lets you rapidly search 8 million ready-to-use data sets in numerical data. Learn how to use it in R with the free Quandl Tutorial.
DataCamp offers free online interactive R courses to on Data Analysis and Statistical Inference and Introduction to Computational Finance.
DataCamp is the fastest way to learn R and data science. Learn in the comfort of your own browser via R tutorials and challenges.
R -Fiddle is a free and powerful tool to write, run and share R-code inside your browser. Include packages to really run R in the cloud.
DataMind is the first free online Interactive Learning Platform for R. Through an in-browser coding environment you can learn R by doing.
Search R documentation and manuals instantly with the help of RDocumentation.
This post summarizes and discusses the results of DataCamp's survey on “R and education”.