twice Multi plots in a page
gridExtra package makes it easier to put multiple plots generated by ggplot2 in a page equivalent to par(mfrow= ).
Example:
http://code.google.com/p/gridextra/wiki/arrange
came across through a conversation in StackOverflow
http://stackoverflow.com/questions/1249548/side-by-side-plots-with-ggplot2-in-r