The font size of menu buttons in the mentioned applications can be adjusted in your .gtkrc.mine like this:
Code:
style "user-font" {
font_name = "Bitstream Vera Sans 8"
}
widget_class "*" style "user-font"
Or: (I've got both, forgot which one sets what exactly.)
Code:
gtk-font-name="Bitstream Vera Sans 8"
This affects the font size and font choice in Gtk-family based applications - namely Firefox, Thunderbird, Pidgin, Gimp, filemanagers like Thunar, PcManFM, Nautilus and so on.
Don't put it into .gtkrc-2.0 - usally, config application from Gnome or theme switcher tools put their options in there and overwrite yours.
The (window?) title font size is adjusted by your windowmanager, if you mean those "titles".
(And wasn't 72 dpi the default xserver setting anyway?)