[R] ggplot2 - plot with only legend?

[Pedro de Barros]

I just found out that this message got scrambled with other threads, 
so I trying to re-send...

Dear R'ers,

I am trying to build a composite plot (with several plots in one
figure). I have tried, but I cannot use facetting, as I need to
customize each plot using grid.
Since all the plots are the same (with different data, but same
layout and categories), I would like to have only one legend, that I
would place in its own viewport, below all the other plots. My questions are

(a) is there is a way, in ggplot, to build a plot that is only the
legend (no data), where the legend occupies the whole viewport;

(b) How can I change the layout of the legend (e.g. have them written
side-by side, instead of over each other).

Thanks in advance,
Pedro