[pmjordan]

You can easily remap it to another modifier key on OSX in the system preferences. Other OSes/Windowing systems typically require a modified keyboard layout, but you might be able to find software to do it easily.

[davvid]

I map caps lock to be an extra control key. It does wonders for vim.

[akamaka]

Thanks for the tip, I just remapped it to control like on the old Sun keyboards. I wish I knew about this sooner!

[djkivi]

KeyTweak is how I do it on Windows: http://webpages.charter.net/krumsick/

[berntb]

Standard function these days under Gnome (Ubuntu, at least).

Ask any Emacs users. :-)