Making good graphics is very important to understand data and to appropriately promote research achievements. ggplot2 is a recent R package of which there are several good tutorial and introductions. But recently a youtube webinar was posted by the very same author of the package, Hadley Wickham. Spending a little time to listen to him is really worthwhile. Click on the picture to go on the page where the video, the slides, and other information are.
Hadley kindly provided the following resources in his slides:
ggplot2 mailing list: http://groups.google.com/group/ggplot2
Lattice to ggplot2 conversion: http://learnr.wordpress.com/s=lattice
Cookbook for common graphics: http://wiki.stdout.org/rcookbook/Graphs/
ggplot2 book: http://amzn.com/0387981403