Making Mac Mail have three screens
“Letterbox is a plugin for Apple’s Mail.app that takes advantage of your widescreen monitor. It rearranges the interface into three vertical columns â€“ so the message pane is to the right of the message list, rather than below. You’ll probably need at least 1280 and perhaps 1440 horizontal pixels for this layout to work well for you.”
I’ve been using it for over eight months now.
Carl: I’m not sure exactly how long I’ve been using mine, but I love it too. :)