here is a simple solution for *NIX & XFree86: use xmodmap and hack the keycode of Caps_Lock to Shift_Lock (YES, the keysym exists :)))
i.e.:

    clear lock
    keycode 66 = Shift_Lock
    add lock = Shift_Lock
[download]

... a similar solution you can obtain on linux console using the tools from console-tools package.

rant: neh, as i 'dislike' Caps_Lock, the same goes for Shift_Lock (ouch, my CapsLock key is quite dusty being not touched for a long time :)) ... but I reckon it can be a little useful =\

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AltBlue .