Mark Kistler also has a new series airing on PBS on Saturdays. You can check your local station for details. And, he has an app for iPhones called "Drawing with Mark Kistler." There are free lessons both on his website and with the app. (And, yes, these are my 4 drawings from today. My favorite was the fish.)
*I am not affiliated with Mark Kistler in any way. I just enjoy his method of teaching art.