Evil Mad Scientist Laboratories - Make a Video Feedback Screen Saver in Quartz Composer
http://www.evilmadscientist.com/article.php/VideoFeedback
"we'll build a video feedback screen saver that can take input from an iSight camera."
Zac's Weblog - Blog Archive Circuit Design With Quartz Composer
http://zacwhite.com/blog/2006/05/23/circuit-design-with-quartz-composer
"Armed with my limited digital design knowledge, I set out to create some well known circuits from within Quartz Composer."