Map Caps Lock to Control in Linux Mint

You can accomplish this with xmodmap. Add the following to ~/.xmodmap:

remove Lock = Caps_Lock
keysym Caps_Lock = Control_L
add Control = Control_L

and run the command xmodmap ~/.xmodmap. You can put this command in whatever startup files are processed by your WM or DE. This will only work in X but it will work regardless of what graphical environment you use.

I found it. It was moved to the regional preferences section:

Go to settings > regional preferences > keyboard layouts > settings and expand the caps lock section.

UPDATE:

In Linux Mint 17.1 you can get to it via;

System Settings > Hardware > Keyboard > Keyboard Layouts > Options > Caps Lock key behavior

No need to use the obsolete xmodmap as there's already an xkb option - namely ctrl:nocaps e.g. in terminal:

setxkbmap -option ctrl:nocaps

With gnome 3 you can either use dconf-editor and add ctrl:nocaps to your xkb-options under org > gnome > desktop > input sources:

or simply enable Caps Lock as Ctrl in gnome-tweak-tool under Typing > Ctrl key position: