This cheat sheet is a quick reference for data wrangling with Pandas, complete with code samples.

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”.