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
KDE's Global Keyboard Shortcuts