Planet Crimson has a nice how to
up reminding us about iPhoto's built-in PhotoBooth effects. The article shows you how to create a sketch-like rendering of your photos by combining filters such as "Colored Pencil" and "Fade Color". The "Sharpen" slider enhances and defines the "pencil" strokes.
Yes, you can do this in Photoshop and yes, it's not ground breaking new image processing research but it's nice to be reminded once in a while about a feature you may have forgotten or overlooked.