Some people prefer to use the Caps Lock key in order to type capital letters, but on linux there's a delay when the button is pressed. Since there appears to be very few people who prefer to type this way the problem has never been fixed.
This is a short and sweet tutorial on how to fix that.
In most distibutions you can do this by pressing the Win/Super key, type terminal
and press Enter.
To generate a keymap type this command and press Enter:
xkbcomp ~/.config/keymap $DISPLAY
Now you need to edit your keymap in your favourite editor.
To open your keymap in gedit type this and press Enter:
gedit ~/.config/keymap
Find the line that looks like:
key <CAPS> { [ Caps_Lock ] };
Replace this code with:
key <CAPS> { repeat=no, type[group1]="ALPHABETIC", symbols[group1]=[ Caps_Lock, Caps_Lock ], actions[group1]=[ LockMods(modifiers=Lock), Private(type=3,data[0]=1,data[1]=3,data[2]=3) ] };
I found this fix thanks to this website: http://askubuntu.com/questions/574740/caps-lock-delay
Now save and exit your editor.
To run your keymap, type this in your terminal and press Enter:
xkbcomp ~/.config/keymap $DISPLAY
You should now have a working caps lock key, however at the moment you would need to run this every time you start the computer.
I need to add some decent instructions here.
For now see this answer on stackexchange.