ways to put multiple graphs on single page (using ggplot2)

I usually have a function like this:

vplayout <- function(x, y) viewport(layout.pos.row=x, layout.pos.col=y)

draw4 <- function(pngname, a,b,c,d,w,h) {
    png(pngname,width=w, height=h)
    grid.newpage()
    pushViewport(viewport(layout=grid.layout(2,2) ) )
        print(a, vp=vplayout(1,1))
        print(b, vp=vplayout(1,2))
        print(c, vp=vplayout(2,1))
        print(d, vp=vplayout(2,2))
    dev.off()
}

#then call it with your graph objects
draw4( "test.png", a,b,c,d, width, height)

-Avram