Hadley Wickham recently updated the ggplot2 package for R to version 0.8.5. In addition to bugfixes and performance improvements, this version introduces some handy new features. Among them: the ability to display mathematical equations as text, automatic legends for color scales, and user-configurable axis labels and legend titles. The Learning R blog runs through the new features with worked examples.
Learning R: New Features in ggplot2 version 0.8.5