Getting Started With R: Some Resources

There are many, many excellent resources for newcomers to R. Here are a few I can personally recommend.

On-Line Introductions and Tutorials

An Introduction to R: In R, run help.start(), then click on "An Introduction to R".
An introduction to many topics. Not very tutorial, however. By Venables, Smith, et al. Also available at http://cran.r-project.org/doc/manuals/R-intro.pdf.
Using R for Data Analysis and Graphics: http://cran.r-project.org/doc/contrib/usingR.pdf
An easy-to-read tutorial. By J. H. Maindonald.
Quick-R for SAS/SPSS/Stata Users: http://www.statmethods.net/
An R language tutorial for people who already know SAS, SPSS, or Stata. By Robert Kabacoff.
Some Hints for the R Beginner: http://www.burns-stat.com/
Click on "Tutorials" to get started with R. By Patrick Burns.

Sources of Help

The R search engine: http://rseek.org/
Looking for something? Start here. This search engine focuses on R-related web sites.
The R Help mailing list: https://stat.ethz.ch/mailman/listinfo/r-help
An incredible amount of Q&A. Got a question? First, search the archives (http://tolstoy.newcastle.edu.au/R/), since it's likely that someone already answered your question. Second, post your question if necessary, but read the posting guide before you do (http://www.r-project.org/posting-guide.html).
Stack overflow: http://stackoverflow.com/questions/tagged/r
Ask a question, get an answer from an expert. Use the "r" tag.
Twitter: http://twitter.com/#search?q=%23rstats
If you can squeeze your question into 140 characters, someone might know the answer. Use the #rstats hashtag.

Books

R in a Nutshell by Joseph Adler (http://www.amazon.com/dp/059680170X)
A combination tutorial and reference book.
A Beginner's Guide to R by Zuur, Ieno, and Meesters (http://www.amazon.com/dp/0387938362)
A quick-start guide for newbies.
Using R for Introductory Statistics by John Verzani (http://www.amazon.com/dp/1584884509)
A good introduction to both R and statistics.
R Graphics by Paul Murrell (http://www.amazon.com/dp/158488486X)
If you want to understand graphics in R, this is the book.
Modern Applied Statistics with S (4th ed.) by Venables and Ripley (http://www.amazon.com/dp/1441930086)
Especially good for anyone who knows statistics and wants to start using R.