R Programming Language

R by example
http://www.mayin.org/ajayshah/KB/R/

R Examples
http://www.rexamples.com/1/R%20Basics

An Introduction to R
https://cran.r-project.org/doc/manuals/r-release/R-intro.html

R Programming – Help, How-To’s, and Examples
http://rprogramming.net/

RStudio
http://www.rstudio.com/