Adam has published a simple and awesome list:
It’s no secret that tech-savvy computer users typically become the go-to guy for all technical help in their circles. More specifically, Mom and Dad tend to always ask us for help with their computers. If you’re tired of the phone calls from Mom and Dad complaining on how sloooww their computer has become, how fast it used to be, how many pop-ups there are, etc., spending hours upon hours fixing and repairing, re-installing and scanning, then this post should convince you with 5 reasons why your parents should use Linux.
=> 5 Reasons your parents should use Linux (foogazi.com)