A collection of frequently used external links is provided .

Links for R and R-Packages

R Project for Statistical Computing – Site to download the R kernel and interpreter
RStudio – Download site for excellent user interface and IDE for R
Comprehensive R Archive Network (CRAN) – Primary source to find and download R packages
CRAN-Mirrors – List of servers hosting R packages for download
CRAN-Task Views – Listing of R packages organized by type – Like CRAN Task Views with additional package listings from BioConductor and GitHub.  Ubuntu Packages for R – Repository for R packages for Linux Ubuntu

Online Resources for R

R-Bloggers – Consolidator of over 750 blogs on R with RSS feed and daily email distribution
R Journal – Journal with many articles on R and R packages with basic to advanced topics
Journal of Statistical Software – Journal with many articles on R packages and methods

Links for R Programming Help

R Help – Online help resource by function
ggplot – Online syntax reference for the ggplot2 package and the Grammar of Graphics