At home I use a keyboard stand (or rather a stand designed for an electric piano), it's adjustable for both sitting and standing, and you can easily put it away.
Wait, what do you put on top of it to hold the (presumably) laptop? I say 'presumably' as you usually need two heights on standing desks: one for the keyboard and one for the monitor which should be higher.
I use a couple of belts, that I can adjust to exactly the right length - to get a good height. The laptop sits in that like a dream and makes for a good laptop desk. With a desktop PC - I just sit the monitor somewhere practical, the keyboard spans the stand it just rests there.
My main desk is actually a drop leaf table. I sit my desktop PC on it. When sitting, the monitor is placed in front of the PC. When standing the monitor goes on top of the PC, and I drop the desk bit.
I'd actually prefer a drop leaf that I could hide the PC in. But currently the PC serves as a good stand for the monitor. It also makes the PC very accessible. The trickier part of my setup is accommodating a mouse. But I could just place a board on the piano/keyboard stand.
