How to deactivate the Caps Lock key on X.org/XFree?

To deactivate the irksome Caps Lock key on X.org, XFree and presumably other X11 servers, the xmodmap utility is used to remove the Caps_Lock keysym from the lock modifier class:
xmodmap -e "remove lock = Caps_Lock"
The xmodmap utility unbinds the Caps Lock key from the lock modifier class temporarily, thus it needs to be executed every time you restart your X session.
To save the changes permanently as the global default, append the xmodmap expression to your global Xmodmap file (usually /etc/X11/Xmodmap). To save them only for your own user, append the expression to your ~/.xmodmaprc file.

How to reconfigure the Caps Lock key on X.org/XFree to do [insert action here]?

There are several actions people would like the Caps Lock key to perform instead of doing the Caps Lock, suggested are (among others) another Ctrl key (Happy Hacker layout) or a second Backspace or Enter key. We assume you already unbound your Caps Lock key from the lock modifier class as described above ("How to deactivate the Caps Lock key on X.org/XFree?").
The key can easily be transformed to another Ctrl key by adding it to the control modifier class: xmodmap -e "add control = Caps_Lock"
To transform it to a second Enter/Return key, overwrite the Caps Lock key's keycode with the Return keysym (keycode 66 on common keyboard layouts): xmodmap -e "keycode 66 = Return"
If you want it to become a second Backspace key instead, replace the Return keysym name in the example above by BackSpace.
See also "How to deactivate the Caps Lock key on X.org/XFree?" on how to make changes permanent.

Thanks for the FAQ, but it doesn't explain WHY the CAPSlock is bad, only how to get rid of it or
alternatives to it.

What's so bad about the CAPS lock? Why should it bother me? Do you know some idea about typing
better that you're not sharing with me?

I already type DVORAK. Are you telling me there's some even better way to type?

There's one language for which Caps Lock is needed - Hebrew. To type Hebrew vowel points (a.k.a. Niqqud) one has to press Caps Lock and then Shift-(Number) to type the vowel. It is quite ridiculous, but that's the de facto standard in Windows and Macs. Ubuntu has a different solution for that (AltGr; not perfect, but better than Caps Lock), but we all know that Windows is far more common.

In fact, it is so ridiculous that few people even bother to type the vowel points. They are not required in most texts, but are sometimes needed.

I already contacted the Standards Institute of Israel with a proposal to change it, but the current situation remains. So please be aware of this in your campaign.

I do not like the idea of removing Caps Lock.

The key is used a lot in programming and there are many more common activities that requires it, such as typing all cap titles. I believe "accidentally" pressing the key is much more the result of poor typing skills rather than the presence of the key, and with any decent typing speed, the mistake can be corrected very fast.

If there was a key that does much more harm than good, it is the sleep key. And I have seen more than one keyboard with that key taken out. I have yet to see a keyboard with caps lock, or any other key taken out.

Almost every key is useful to the people concerned and/or in special circumstances. For example the menu key is normally never used but can be very helpful if the mouse is broken.

I do not like the idea of heavy customization by remapping of keys because it breaks the standards and prevents one from typing on any keyboard that comes about. Software designers also need to know how does the keyboards of their users look like to conveniently map the functions.

Keyboard layouts are suited to functions, not individuals. There can be a different keyboard for every position or language, but not for every person. If one is truly comfortable with one particular layout, then it does not matter what symbol the manufacturer decides to print on the keys. Some people actually find blank keyboards to be better.

Regarding "What's so bad about Caps Lock?", I can think of a few things…

1. It's an anachronism. Much like the QWERTY layout and the staggered placement of keys, Caps Lock hearkens back to the days of manual typewriters, when the Shift key literally moved either the platen (floating shift) or the type elements (basket shift) to a higher position. The Shift Lock key (as it was then known) was designed to relieve stress on the fingers from holding down Shift keys. With the advent of electric typewriters, the need for this function became less primal, as Shift keys no longer required more force to hold down than any other key. But as with all things, the inertia of success pretty much dictated that the key would remain on the ISO-standard keyboard to this day, and would continue to be placed directly over the leftmost Shift key.

2. It's relatively useless in English. Maybe if it had remained a SHIFT lock, it might have still had a function of sorts (the symbols over the number keys would be easier to type rapidly, which can be more useful that all-caps text). As it is, the only function of Caps Lock is to ensure you type only capital letters. As noted in a comment above, this is useful in certain programming languages, albeit mostly of an older vintage (COBOL, Fortran, etc.), but for those who primarily use a keyboard to write in English it seems like a boondoggle.

3. It's too easy to hit by accident. Granted, this can be attributed more to its placement on the home row (or sloppy typing habits) than any inherent fault of the Caps Lock function itself. Still, it's just a bit too easy to hit Caps when you're trying to hold down the left Shift key or Tab, and making matters worse is that there usually isn't a visual or aural cue that you've hit the key; in most cases you only notice it when you reach for the sHIFT KEY AND YOUR TEXT STARTS COMING OUT LIKE THIS, BECAUSE YOU HIT cAPS lOCK INSTEAD. Quite annoying, as you can see.

4. Ergonomically, there are better keys that can be put here. The most common "replacement" for Caps Lock is to have a Control key there instead, as was the case on some early computers and UNIX workstations. I also like the idea of a secondary Backspace or Enter key in place of Caps, which would speed up typing and correcting spelling errors (the latter of which currently requires a somewhat awkward jump). Strictly speaking, there's little to no reason (other than typewriter tradition) for Caps to be where it is, and every reason for other, more generally useful keys to be in that position.