screenshot: apple + shift + 4
After some research i found this blog, which perfectly detailed explains how to get this hidden setting:
Open the system preferences Hold down the command and option keys while clicking the display icon Next locate the screen adjustments on the external monitor and you will notice now there is an option called "Rotation". Choose 90 Degrees and now your monitor is in portrait mode.
looks cool.. investigate more..: http://brian.io/lawnchair/