If the Debian package of the day website were still alive, I would post this there. Since I still have the backups lying in my harddrive waiting to be restored in some other place, I'll post here.
In the graphviz package
there is a neat shell script called
vimdot that will open
vim and a X window showing your progress with the drawing, updated
each time you save. Simple but really useful, probably not much people know it