Regular reader Pat sent along some information on ShortCourses.com. They have several online books
Welcome to ShortCourses.com,
Famous for its books on digital cameras and digital photography.
THE digital photography resource for over 6,000,000 visitors a year
I quickly glanced over a couple of the “courses”. As of the time of this writing, there seems to be 9 courses, along with several other useful resources. Check it out!