User has to select a link
Show a partial menu with "expand" capabilities
Very full web pages with secondary navigation. You have the main menu but there are also other menus that do not fit with the main menu.
Present a list of links that come from the menu and allow the users to see all links. When users click on the "expand" link the entire list is show, either on a new page or by moving down other items below.
The teaser menu shows what kind of things the users are able to find without showing them all. This saves spaces and increases the information "scent" of the menu label.
A variation at www.zibb.nl