here is a simple way to shrink down the sizes of your fonts and menus in openoffice3:

fonts:
echo "Xft.dpi: 80" > ~/.Xdefaults
change the 80 to a size that fits you best
edit 20-nov-2008: this will obviously override .gtkrc & .gtkrc-2.0

menus:
open any oo program
tools —> options —-> OpenOffice.org —-> view
change “icon size and style”
done