Apple Mac OSX, keyboard shortcut to lock screen

A common question from switchers to OSX from another operating system, is how they lock the screen with a keyboard shortcut.

There is no built in method, but there is a free addon that does it for you: LockTight which you can get here http://www.gkoya.com/2006/11/23/locktight-for-mac-os-x-intel/

Update: I accidently deleted the startup item to make LockTight available on start. I discovered that you can replace it by navigating to:

~/Library/PreferencePanes/LockTight then right click or CTRL click, select 'show package contents' then go to Contents/Resources and look for 'SleepTightAgent'.

If you place this in StartUp items it will be available from startup.