I never use Caps Lock, so I disable the Caps Lock key completely with xmodmap, to avoid hitting it by accident.

Occasionally my X server gets into caps-lock state anyway. (Usually some complicated stunt was involved, like attaching x11vnc to the display remotely.) And then I can't turn it off again using the Caps Lock key.

So I wrote a tiny X client that lets me type 'xcapslock off' at a shell prompt …

… and then I had to make an alias to it, called 'XCAPSLOCK OFF'.

@simontatham I remapped mine to <compose>, which is occasionally useful and a lot less annoying when you aim for the <a> mid-sentence and miss.
I then mapped both-shift-keys-at-the-same-time to toggle capslock, for the occasional moment when I WANT TO TALK LIKE AN ANTHROPOMORPHIC PERSONIFICATION.

As this is Linux, I've long since forgotten how I achieved either of these things.