Related to my other question on Windows, how would one go about creating a logoff script for Mac OS X?
What do you mean by "logoff script"? If you mean "how to logoff current session from the terminal", then you can do this from any shell script or terminal:
If by "logoff script" you mean "a script that is executed when one logs off", then I invite you to read this nice post on that topic (with example scripts): http://www.bombich.com/mactips/scripts.html, or see the official documentation here: http://support.apple.com/kb/HT2420?viewlocale=en%5FUS
Another very nice example: http://www.macosxhints.com/article.php?story=2006081701162739