legend for several graphics

Hi,

I am trying to generate a figure of 9 plots that are contained in one
device by using

par(mfrow = c(3,3,))

I would like to have 1 common legend for all 9 plots somewhere outside
of the plotting area (as opposed to one legend inside each of the 9
plots, which the function legend() seems to generate by default).

Any hint how to do this?

Best,

Georg