Some R documents/packages I came across recently:

Some extra geoms, scales, and themes for ggplot -- https://github.com/jrnold/ggthemes

A document on R Markdown -- http://arxiv.org/pdf/1501.01613v1.pdf

Intro to dplyr -- http://seananderson.ca/2014/09/13/dplyr-intro.html

How to re-create in R a Tufte's weather map - https://rpubs.com/bradleyboehmke/weather_graphic