Using CapsLock to switch the keyboard language layout

Following @Bob's suggestion to use AutoHotkey, the following script will simulate Alt+Shift when you press CapsLock:

CapsLock::Send, {Alt Down}{Shift Down}{Shift Up}{Alt Up}

Windows can be a little stubborn when it comes to keyboard shortcuts only consisting of modifiers, but the above technique works.

In windows you can set Windows to use Grave Accent (`) for switching between languages or keyboard layouts via a single key press.

If your windows is set to change keyboard layout by Ctrl+Shift you can use following AutoHotKey script (I strongly recommend using http://www.autohotkey.com/) to map them to Caps Lock, normal CapsLock will be achieved by Shif+CapsLock

SetCapsLockState, AlwaysOff
+CapsLock::CapsLock

CapsLock::Send, {Ctrl down}{Shift down}{Shift up}{Ctrl up}{Ctrl up}
return

Use lswitch.

Use any key to switch input languages, usage: lswitch [keycode]. Keycode is optional and defaults to context menu key. Another good candidate is a CapsLock key with a keycode of 20.

Cheers!