Here is a little script which will display a list of the printers setup on the computer and ask that you select which one should be the default. I created the script because certain applications the students where printing from automatically used the default printer, and did not display a standard print dialog window. This of course caused print jobs to go all over because the kids did not know which printer was the default.
So basically I took this script, added a line at the end which opened the offending application (application "suchandsuch" activate), and copied the offending application's icon to the script. So the kids think they are opening the normal app, but really they are running my script. How sneaky!
Updated to work under OS 10.5