Head over to Revolutions Blog for a list of PDF and powerpoint resources for making the transition to R from other programming or stats languages. All of these notes come from the New York R meetup. I enjoyed browsing the meetup's files - lots of powerpoints, PDFs, and example R data files for various topics, including several slideshows on ggplot2. Don't forget the ggplot2 tutorial I posted here earlier this week if you're completely new to ggplot2.
If you're coming from SPSS or SAS, I've read good things about Robert Muenchen's book R for SAS and SPSS Users, which can be found on Amazon (~$50), or downloaded for free from http://rforsasandspssusers.com/.
Revolutions: Coming to R from SQL, Python, SAS, Matlab, or Lisp