On a spur-of-the-moment decision, I decided to create an overlay on Google Maps that shows every LDS mission. If you served an LDS mission and think you know the current mission boundaries, do me a favor and go to http://tinyurl.com/ldsmissionmaps. On the left, you should see "LDS Mission Maps", and near it an "Edit" button. Click that, and you should see some shape-drawing tools appear on the map itself. If your mission's not on the list, find it and draw a shape around it, then list its name. (Preferably the standard name in English, as in "Spain Malaga Mission", with the country first.)
Oh, and don't be afraid to change the color so that it stands out from its neighbors!