Taken from Section 5 (Add-On Packages) of the R FAQ (general):
http://cran.r-project.org/faqs.html
http://cran.r-project.org/doc/FAQ/R-FAQ.html
http://cran.r-project.org/doc/FAQ/R-FAQ.html#R-Add_002dOn-Packages
5.1.1 Add-on packages in R
The R distribution comes with the following packages:
base
Base R functions (and datasets before R 2.0.0).
compiler
R byte code compiler (added in R 2.13.0).
datasets
Base R datasets (added in R 2.0.0).
grDevices
Graphics devices for base and grid graphics (added in R 2.0.0).
graphics
R functions for base graphics.
grid
A rewrite of the graphics layout capabilities, plus some support for interaction.
methods
Formally defined methods and classes for R objects, plus other programming tools, as described in the Green Book.
parallel
Support for parallel computation, including by forking and by sockets, and random-number generation (added in R 2.14.0).
splines
Regression spline functions and classes.
stats
R statistical functions.
stats4
Statistical functions using S4 classes.
tcltk
Interface and language bindings to Tcl/Tk GUI elements.
tools
Tools for package development and administration.
utils
R utility functions.
These “base packages” were substantially reorganized in R 1.9.0. The former base was split into the four packages base, graphics, stats, and utils. Packages ctest, eda, modreg, mva, nls, stepfun and ts were merged into stats, package lqs returned to the recommended package MASS, and package mle moved to stats4.
#### Apr. 9, 2013 for R 3.0.0 for Windows