(I’m posting this mostly for my benefit, but hopefully someone else was looking for a quick and easy solution as well.)
Have you ever wished OS X had the equivalent of Windows' control-alt-delete so you could quickly lock your computer before you step away? My friend Andre did, and he found this solution on the OS X Hints site that allows you to lock your screen from the Terminal. We took part of that script and threw it into an Automator workflow for easy access. Just move the file into
~/Library/Services/, and you can assign it a hotkey in the Keyboard system preference pane.
For reference, here’s the terminal command that the script runs: