How can I show the login window after a period of inactivity?
One solution could then be this one...

Download this ScriptSaver (ScreenSaver): http://swannman.wordpress.com/projects/scriptsaver/ - which can run AppleScripts.

Then write an AppleScript script with this content:

tell application "Finder"
    do shell script "/System/Library/CoreServices/Menu\\ Extras/User.menu/Contents/Resources/CGSession -suspend &gt; /dev/null"
end tell


Setup a ScreenSaver in "Desktop &amp; Screen Saver", and configure this with the ScriptSaver, which you then setup with the AppleScript script from above.

After min. 3 minutes the current user session will be switched to the Fast User Switching window.