I discovered an article on setting focus on the next field after a selection is made in a select option menu thingo, which looks pretty handy to have around. It could potentially be a bad thing, too, (if the user selected the wrong option + does repeatedly), but generally speaking this looks like a handy piece of code to have around.
It seems handy, too, for such fields as telephone numbers, where the focus goes to the next field, after the user enters three numbers (or four, whatever the case may be).