Update 2008-12-15: Clarified some stuff, removed screenshots.

If you, like me, switch between different keyboard layouts on a daily basis, you are sooner or later going to ask yourself something like “which layout is currently active”? When logged in, this is easy to conclude - just make sure that the input menu is shown in the menu bar. You can enable this feature in the International pane in System Preferences. That done, you’ll end up with a new icon in you main menu bar, displaying a flag representing the currently active keyboard layout.

So far, so good. But what about when you’re logged out? Or when the screen saver is active? Turns out that Apple thought about this problem too; just fire up System Preferences again and go to the Account pane. Make sure Show Input menu in login window is checked, and the login screen window (and the screen saver lock window) will be equipped with a drop down menu indicating which layout is currently active (and the possibility for you to change the the layout).

Now there’s no excuse for all you Swedish Objective-C programmers to switch between US/Swedish layouts ;)