AddMessage(format("( %s ) %i,%i",
GetZoneText(),px *100,py *100));
(As commenters have noted, the formatting is weird here on the blog-- it's meant to be two lines, both starting with script. The other line breaks will need to be taken out.)
Just put that on a button, call it "Where am I?" or something like that, and then click it to get your current ingame coordinates in the chat channel. Considering how poor my addon-updating abilities are, that's perfect.
Of course, there are lots and lots of addons floating around that will do this even better-- showing your coordinates and cursor coordinates in the window, and all kinds of other ways. But if you only use coordinates every once in a while, and never remember to update your addons, this little macro could be pretty useful to have.