This tutorial is intended to introduce users quickly to the basics of R, focusing on a few common tasks that biologists need to perform some basic analysis: load a table, plot some graphs, and perform some basic statistics. More extensive tutorials can be found on the project website and via bioconductor (not covered here).
You can add more tutorial links in comments if found new pages.
You can also look at this R tutorial http://www.burns-stat.com/pages/Tutor/R_inferno.pdf
I found one R package SeqinR very handy in statistical computing of NGS data.
SeqinR 2.0-1: a contributed package to the project for statistical computing devoted to biological sequences retrieval and analysis
Memory efficient string containers, string matching algorithms, and other utilities, for fast manipulation of large biological sequences or sets of sequences. http://www.bioconductor.org/packages/2.12/bioc/html/Biostrings.html
For video R tutorial you can visit youtube http://www.youtube.com/playlist?list=PL69A9CCD816A5F3A5
The book "Applied Statistics for Bioinformatics using R" provide an introduction into statistics in order to solve some problems of bioinformatics.
DotPlot for Protein Sequences using R @ http://www.biogem.org/blog/dotplot-for-protein-sequences-using-r/
Frequency Plot for Protein Sequences using R @ http://www.biogem.org/blog/frequency-plot-for-protein-sequences-using-r/
Applied Statistics for Bioinformatics using R @ http://cran.r-project.org/doc/contrib/Krijnen-IntroBioInfStatistics.pdf
R tutorial by Division of Molecular Biology, Netherlands Cancer Institute http://bioinformatics.nki.nl/courses/Rstat_12_I/texts/resources/R-intro.pdf
Introduction to Feature selection for bioinformaticians using R, correlation matrix filters, PCA & backward selection http://computationalproteomic.blogspot.co.uk/2013/10/introduction-to-feature-selection-for.html?
useR! 2013 R / Bioconductor for Analysis and Comprehension of High-Throughput Genomic Data http://bioconductor.org/help/course-materials/2013/useR2013/Bioconductor-tutorial.pdf
RGL: A R-library for 3D visualization with OpenGL http://rgl.neoscientists.org/arc/doc/RGL_INTERFACE03.pdf
R by example http://www.mayin.org/ajayshah/KB/R/
You can find useful R video tutorial @ http://www.youtube.com/watch?v=iffR3fWv4xw&list=PLOU2XLYxmsIK9qQfztXeybpHvru-TrqAP
The illinois R tutorial http://math.illinoisstate.edu/dhkim/rstuff/rtutor.html
The basic stats with R at http://ww2.coastal.edu/kingw/statistics/R-tutorials/
You can also find list of several online R tutorial around the world at http://pairach.com/2012/02/26/r-tutorials-from-universities-around-the-world/
SimpleR tutorials is very lucid and practical for general data analysis with R. http://cran.r-project.org/doc/contrib/Verzani-SimpleR.pdf