We have a few spare monitors laying about at work, and I just grabbed one with a rotating stand, so I can switch it between Landscape and Portrait. This is nice, because it's got more pixels than my laptop's built-in screen, and it's also larger.

It's also very handy when viewing pages that are narrow and tall.

All I need now is a way to quickly switch the screen's orientation without digging through a GUI. This looks like a job for xrandr and KDE's Global Keyboard Shortcuts

I've created two Custom Shortcuts in my KDE, called "screen left" and "screen normal". For "screen left"

In the Action tab, specify a Command xrandr --output VGA1 --rotate left
In the Trigger tab, specify a shortcut key. I'm using Meta+Alt+F10

Do the same for "screen normal" substituting --rotate normal, and a different key — Meta+Alt+F9 in my case.

Of course, the --output switch will vary per machine, depending which screen you want to rotate and how it's connected. My laptop is connected to two screens, one via a VGA cable, and one via HDMI. I got the output name by just running xrandr with no arguments and looking for the string " connected":

mjl@milo:~> xrandr|grep " connected"
LVDS1 connected (normal left inverted right x axis y axis)
HDMI1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 531mm x 299mm
VGA1 connected 1680x1050+1920+0 (normal left inverted right x axis y axis) 434mm x 270mm
mjl@milo:~>

So this shows VGA1, HDMI1 and LVDS1 (which is the laptop's built-in screen, and is connected but disabled when driving two external monitors).

Have a lot of fun!