I’ve been using ggplot2’s facet_wrap and facet_grid feature mostly because multiplots I’ve had to plot thus far were in one way or the other related. However, I needed to plot a multiplot consisting of four (4) distinct plot datasets. In the past, when working with R base graphics, I used the layout() function to achive this [1].
A quick search online initially resulted in this [2] tutorial that involves creating a new function; and interesting these [3, 4] blog posts that propose using the gridExtra package [5].
Install gridExtra
install.packages("gridExtra")
Generate individual plots and arrange in grid
# define individual plots p1 = ggplot(...) p2 = ggplot(...) p3 = ggplot(...) p4 = ggplot(...) # arrange plots in grid grid.arrange(p1, p2, p3, p4, ncol=2)
Sample output is below.

[1] http://lightonphiri.org/blog/r-graphical-representation-multiple-plots-in-one-graph
[2] http://www.cookbook-r.com/Graphs/Multiple_graphs_on_one_page_(ggplot2)
[3] http://mcfromnz.wordpress.com/2011/06/09/gridextra-multiple-plots-from-ggplot2
[4] http://www.imachordata.com/extra-extra-get-your-gridextra
[5] http://cran.r-project.org/web/packages/gridExtra