Writing from the previously mentioned intro to R course at the Kennedy Center. If you couldn't make it you can download all the course materials from Theresa Scott's website, under the "Current Teaching Material" heading. Here is a direct link to the PDF for the overview materials that we're going over today, along with the R code from the examples in this guide. This guide is suitable for someone who's never used R before, and gets you up and running with the basics of the language, importing/manipulating data, generating basic descriptive statistics, and graphing. There's also a part II (which isn't being covered in the course today) that goes into more detail on the language, lower-level graphing commands, and has a very useful dictionary (Ch. 3) of commonly used functions broken down by topics and uses. Theresa also has tutorials on using LaTeX and R with Sweave on this website.
If you didn't get in the course off the waiting list keep an eye out on the Kennedy Center calendar of events to see when this course will be taught again.