What documentation exists for R?

Chapter 5: R Add-On Packages 52
paleoTS Modeling evolution in paleontological time-series.
pamr Pam: Prediction Analysis for Microarrays.
pan Multiple imputation for multivariate panel or clustered data.
panel Functions and datasets for fitting models to Panel data.
papply Parallel apply function using MPI.
partitions Additive partitions of integers.
partsm Periodic AutoRegressive Time Series Models.
party Unbiased recursive partitioning in a conditional inference framework.
pastecs Package for Analysis of Space-Time Ecological Series.
pbatR Frontend to PBAT to run within R.
pcaPP Robust PCA by Projection Pursuit.
pcalg Standard and robust estimation of the skeleton (ugraph) of a Directed Acyclic
Graph (DAG) via the PC algorithm.
pcurve Fits a principal curve to a numeric multivariate dataset in arbitrary dimensions.
Produces diagnostic plots. Also calculates Bray-Curtis and other distance matrices
and performs multi-dimensional scaling and principal component analyses.
pear Periodic Autoregression Analysis.
permax Functions intended to facilitate certain basic analyses of DNA array data, especially
with regard to comparing expression levels between two types of tissue.
permtest Permutation test to compare variability within and distance between two
groups.
perturb Perturbation analysis for evaluating collinearity.
pgam Poisson-Gamma Additive Models.
pgirmess Functions for analysis and display of ecological and spatial data.
pheno Some easy-to-use functions for time series analyses of (plant-) phenological data
sets.
phpSerialize
Serialize R to PHP associative array.
pinktoe Converts S trees to HTML/Perl files for interactive tree traversal.
pixmap Functions for import, export, plotting and other manipulations of bitmapped
images.
plm Linear models for panel data.
plotrix Various useful functions for enhancing plots.
plugdensity
Kernel density estimation with global bandwidth selection via “plug-in”.