The Best Way to Cool your Coffee

Now you know.  Bottom line: stirring with a spoon is best, unless you have a cup and saucer, in which case:
If you want an even faster way to cool a cup of coffee, here's a tip from my Granddad Parker: forget the spoon and saucer your coffee. In other words, pour the top part of it from the cup into a saucer, and then back again a few times. The large and constantly changing surface area during this process will cause extremely rapid evaporation of those high-energy outliers, much faster than stirring. Saucering was very common up through the Great Depression, which is one of the reasons older coffee sets always included saucers. You also get deep-ish saucers at many restaurants as a holdover from this practice, although I doubt many people do it any more.  
I think "looking like a ridiculous holdover from the Grapes of Wrath days" is probably the reason most people don't "saucer" anymore.

Of course, if you're like me and you order it with "THREE! not two, not four...THREE!" ice cubes, you won't have this problem to begin with.  And, believe me, after you've done this two or three times in a row, the girl behind the counter will remember you.