Presumably for the keyboard layout currently being used. There's probably a checkbox to show the input menu in the menu bar in the System Preferences -> International pane; I'd dig around there.
I know what you're talking about. It's to do with localization/language.
Go to System Preferences.
Then click Language & Text
Then click the Input Method Tab
Tick the box at the bottom right - show input menu in menu bar.
Then you'll get a lovely flag in the top corner. Which is incidentally right where Gerrard is going to put the ball tomorrow. A 30 yard screamer in the top corner!