The menu has options to lock the screen, log out and shutdown, but there isn't an option that allows me to switch to a different user. Is there another way to do that or, even better, is there a way to add that option to the global menu? I am using Ubuntu 11.10.
One suggestion is to create either a favourite shortcut in the main menu or a panel shortcut.
To do this, use
Logout and login
Then search for your shortcut:
Right-click the menu item and choose one of the options as shown.
on linux mint 13 cinnamon there's a "New Login" program go to Menu --> search "new login" --> enter it should open the mdm login window