http://winetricks.googlecode.com/svn/trunk/src/install-gecko.sh now also installs mono.
It should be probably be called wine-install-addons.sh now, maybe I'll rename it that soon. If you have a better idea for the name, let me know.
(I've also deprecated the copy that was in winezeug; that one now just tells users to get it from the winetricks repo.)