Less than 24 hours after Ted Stevko mentioned a trick at his OS X Con preso, I've already put it to good use several times. Here it is for posterity:
In Panther, when a Save dialog is displayed, type / to display the "Go to the folder" dialog so you can type in a path.
In my notes from the talk, I have that Ted said the shortcut was Control-/, but it seems that Control really isn't necessary. YMMV.