This website provides a simple summary of the theme elements that can be set within ggplot2. There should be sufficient information here to change the default settings for graphs within the ggplot2 package.
There are the following book reviews on this website:
Book Review – Modern Applied Statistics with S by W. N. Venables and B. D. Ripley (Springer 2003)
Book Review – ggplot 2: Elegant Graphics for Data Analysis by Hadley Wickham (Springer 2009)
Book Review – Lattice: Multivariate Data Visualization with R by Deepayan Sarkar (Springer 2008)