Notes on R
Documentation:
The R-project's intro: Introduction to R
(nice, but not everyone finds it the "user-friendly")
A short intro to R: R_Handout
(thanks to a student who contributed this)
Peter Rossi's intro to R: Rossi notes on R
(everything Rossi writes is good!)
My MBA data-mining lecture notes on R:
Plots Tables and Trees (in R) (don't read the part on Trees)
More on R
Script for learning R: learn_R.R