This is one of the rare ones that I planned exactly how I wanted it, and set out to make it look as it did in my mind. Most of my art projects happen by serendipity.
* Please see note at bottom re use of my photo.* My main point in this tutorial is to show you how I reproduce the illusion, and that isn't software specific! Since you're most certainly using a version newer than 7, your screen will vary slightly from my screenshots. This tutorial was written for Photoshop version 7, though it will work fine any version, and probably other software, too.